Global Atmospherics Inc. Joins Vaisala the Scope and Future Of

159/2002

Vaisala expands into lightning data services Global Atmospherics Inc. joins Vaisala

The Scope and Future of Nowcasting

Meteorological studies in the marine Arctic The Arctic Ocean 2001 Experiment Contents

The US Air Forces used TMOS (Vaisala President’s Column 3 TACMET Systems) at the 2002 Winter Olympics for real-time meteorological data Remote Sensing from the sports venues. The support for medical Global Atmospherics Inc. Joins Vaisala 4 and security aviation operations came from the extensive weather support system at the Upper Air Olympics in which meteorologists from Arctic Ocean 2001 Expedition 6 government agencies, private companies and Measurement Accuracy the University of Utah cooperated to provide accurate and timely weather information. and Repeatability of RS90 11 RS80 Humidity Data Set Corrections 14 Vaisala Launches the RK91 Rocketsonde 16 Nowadays, a number of systems provide dynamic advice to motorists on the real-time Development of Light Meteorological status of the road network. Most commonly Sounding System M200 17 real-time information on congestion allows drivers to take alternative routes to reduce Surface Weather travel time. Road weather systems and USAF TMOS at 2002 Winter Olympics 18 variable message signs are also used to improve road safety, for example by the Roads MAWS Enhanced with New Features 21 and Traffic Authority of New South Wales in Australia. With the help of dynamic warning MAWS AWSs to Synoptic Stations in Poland 24 signs driving speed can be adjusted as weather FS11 Visibility Sensor Launched 25 conditions change. Aviation Weather LD40 Ceilometer Launched 26 Driving safety is a key concern for road Romanian Air Force Choose AW11 26 authorities. Other than the weather, one of the most interesting factors which affects safety is a Vaisala AWOS System to Helsinki-Vantaa Airport 27 vehicle’s grip, i.e. the friction between a Road Traffic Weather vehicle’s tires and the road surface. Together with the Finnish Road Administration Field Trial of Vehicle Grip Compared Vaisala conducted a field trial in Southern to RWS Data 28 Finland during the winters of 1999-2000 and 2000-2001, to study which measurement Dynamic Warning Signs Act as Signs of Rain 30 results best indicated a vehicle’s grip. Additional Features Role and Scope of Nowcasting 33 Two German Scientists win Professor Vilho Vaisala Award 38 Cover photo: Vaisala at AMS 2002 38 Summer scenery at Nagu guest harbor on the Vaisala Centralizes USA Manufacturing Finnish archipelago. Photo by Mauri Rautkari, Operations 39 Lehtikuva. Editor-in-Chief: Design and Artwork: Marit Finne Edita Oyj (absent on study leave June 1, 2001 - July 15, Editors: 2002) Bellcrest Language Services Oy Acting Editor-in- Chief: Printed in Finland by Ritva Siikamäki Edita Oyj, Finland

ment, improved safety and bet- Publisher: ONM IR EN Vaisala in Brief NV T E A ter performance. Vaisala Oyj , P.O. L IC L Box 26 D A – We develop, manufacture and B R

FIN-00421 Helsinki L market products and services for – We focus on market segments N environmental and industrial where we can be the world leader, FINLAND measurements. the preferred supplier. We put a Phone (int.): high priority on customer satis- +358 9 894 91 441 002 Printed matter – The purpose of these measure- faction and product leadership. Telefax: ments is to provide a basis for a We secure our competitive advan- +358 9 8949 2227 better quality of life, cost sa- tage through economies of scale Internet: ISSN 1238-2388 vings, protection of the environ- and scope. http://www.vaisala.com

2 159/2002 President’s Column

Towards a new generation of high-precision forecasts

n the past decades, efforts to develop weather forecasts I have focused on long-term forecasts, the range of which extends from five or six days to up to seven days. Less attention has been paid to short-term high- precision local forecasts, nowcasting and mesoscale services. In many applications, however, a high-precision local fore- so there. A radical change could a long time, and we have appre- cast, pertaining to short term lo- be about to happen, similar to ciated their benefits. Conse- cal conditions, is the most use- the one that took place in the quently we believe that high-pre- ful. Application-specific weather telecommunications sector cision weather forecasts have a observation systems for the when it moved from line teleph- larger market to conquer, includ- needs of aviation and road traf- ony to mobile communications. ing the general public. We have fic have already been available The question is, however, made a focused investment in for a long time and defense whose business would the provi- the observation technologies forces too now have their own sion of such a service be? Would that high-precision weather fore- nowcasting applications. Nowa- it fall in the domain of national casting require, with lightning days, ever-increasing invest- weather services or would it be detection and wind profilers be- ments are also being made in the business of the private sec- ing the most recent examples. weather systems for the needs of tor? How would the products be Long-term forecasts and the agriculture. Many other profes- traded? Would the consumer synoptic observations for them sions benefit from high-preci- pay for them, would the field be will naturally always be needed. sion weather forecasts. So even open for sponsoring or advertis- They form the very basis of all does Everyman, for example ing, or should the money come weather services. But high-preci- when planning leisure activities. from public funds? This seems sion forecasts could comple- In my opinion, the time is to be where the dilemma lies. ment them in an excellent man- starting to be ripe for the broad What will be the business idea ner, and to a much greater extent and large-scale provision of now- and earnings principle? It will be than is the case today. G casting and mesoscale forecasts. established. It is time for pio- We have forecast models, and neers to step up. the required observation meth- Vaisala has been active as a ods already exist. I believe that supplier of application-specific Pekka Ketonen the market for such services is al- weather observation systems for President and CEO

159/2002 3 Ritva Siikamaki, MA Acting Editor-in-Chief, Vaisala News Vaisala Helsinki Finland

Vaisala expands into lightning data services Global Atmospherics

Inc. joins Vaisala NLDN communications work as follows: 1) Sensors detect lightning and transmit the data to a satellite, 2) The In March 2002, Vaisala acquired Global Atmospherics satellite relays the Incorporated of Tucson, Arizona, USA, from the Sankosha Group. information to earth stations, 3) Data are Global Atmospherics is the world’s largest lightning detection transmitted to the Network equipment manufacturer and lightning data services operator. Control Center via landlines, 4) The Network Renamed as Vaisala-GAI Inc., the company is now part of Vaisala’s Control Center processes the Remote Sensing Division. This acquisition strengthens Vaisala’s data, 5) The processed data are relayed back to the lightning and thunderstorm detection expertise and expands the satellite, 6) Lightning data product selection offered to clients whose operations are appear on user’s display across the country within affected by severe weather. seconds of occurrence.

4 159/2002 aisala-GAI is the lead- Director of the Remote Sensing ing manufacturer of Division, stresses that there are V standalone lightning remarkable synergies in combin- detection instruments and LF ing the two lightning detection (Low Frequency) lightning de- network product lines into one tection networks and has also re- business unit. The combination cently developed VHF (Very will provide optimized systems High Frequency) lightning de- for the varied needs of lightning tection technology. The compa- detection network clients. ny owns and operates a national The Remote Sensing Divi- pany was a subsidiary of the The management of Vaisala- lightning sensor network in the sion focuses on two new and ex- Sankosha Group of Japan. GAI Inc at a meeting in Tucson. From the left: Martti U.S. and sells various lightning panding fields of atmospheric Real-time lightning data Husu, Philippe Richard, Jack data products to the U.S. Na- measurement: nowcasting and Nelson, Michael Austin, tional Weather Service, airports, meso-scale forecasting. These are nationwide in the U.S. Ellen Carolan, Rich Pyle and power utilities, recreational facil- fields where severe weather phe- Since 1989, the NLDN® has Ken Cummins. ities, insurance companies and nomena which rise within a rela- monitored the 20 to 25 million weather service providers. The tively short time, like thunder- cloud-to-ground lightning company also participates in storms, windshear, local rainfall strikes that occur every year in August 2001. This lightning lightning data services in Cana- and hailstorms, can be predicted. across the contiguous 48 states. detection network covers the da, France, Central Europe and Following the acquisition of NLDN® consists of over 100 re- greater part of the European the Benelux countries. Global Atmospherics Inc. and mote, ground-based sensing sta- continent. EUCLID is capable the previous acquisition of Di- tions located across the United of tracking lightning by mapping Comprehensive remote mensions SA, Vaisala will elevate States which detect the electro- up-to-the-second lightning activ- sensing and lightning to a global market leadership po- magnetic signals given off when ity throughout Austria, Belgium, detection expertise sition in the field of lightning de- lightning strikes the earth’s sur- Czech Republic, France, Ger- In early 2000, Vaisala acquired tection and localization. face. These remote sensors send many, Hungary, Italy, Luxem- another lightning detection net- the raw data via a satellite-based bourg, Netherlands, Norway, work manufacturer, Dimensions Vaisala-GAI’s history communications network to the Poland, Slovakia, Slovenia, and SA of France, which also part of Vaisala-GAI was founded in Network Control Center operat- Switzerland. The network uses the Remote Sensing Division of 1976 by three University of Ari- ed by Vaisala-GAI Inc. in Tuc- 85 ground-based sensors that de- Vaisala. It is currently the lead- zona scientists, Dr. E. Philip son, Arizona. Within seconds of tect and then report detailed in- ing manufacturer of VHF tech- Krider, Dr. Burt Pifer, and Dr. a lightning strike, the NCC’s formation on each lightning nology Total Lightning Detec- Martin Uman, who began re- central analyzers process infor- event to a single, central proces- tion Networks. Mr. Martti Husu, searching lightning properties mation on the location, time, sor. The network then provides and behavior in the mid-1970’s. polarity, and amplitude of each accurate and reliable informa- Over the next decade their re- strike. The lightning information about the cloud and cloud- search, combined with the con- tion is then communicated to to-ground lightning strikes to The National Lightning tributions of others, resulted in users across the country. Light- each member. Detection Network® locates the development of the United ning data users in the US in- strikes across the U.S. in States’ only national lightning clude the National Weather Ser- Preparing for storm seconds. The network operates hazards 24 hours day, 365 days a year. detection system, the U.S. Na- vice (NWS), the Federal Avia- Pictured is the control center at tional Lightning Detection Net- tion Administration (FAA), the Lightning information is critical the Vaisala GAI Inc. office in work® (NLDN®). At the time of National Aeronautics and Space for weather forecasters and Tucson. acquisition by Vaisala, the com- Administration (NASA), the weather-sensitive businesses, Weather Channel® and PGA such as airport operators and air TOUR®, as well as major power traffic controllers, electric power companies, airports, and thou- utilities, mission critical facili- sands of businesses nationwide. ties, golf courses and outdoor NLDN data is accessible to sub- sports facilities. They closely scribers through various DOS, watch storm development so Windows®, or Unix® based dis- that they can be prepared for play and analytical software. storm hazards. When a storm starts generating lightning the European cooperation lightning alerts forecasters to in lightning detection watch the thunderstorm for oth- Operators of Vaisal-GAI lighter dangerous weather elements ning information system tech- that often occur with electrified nology in Europe established storms, for example heavy rain, the European Cooperation for hail, flash flooding, high winds, Lightning Detection (EUCLID) downbursts, and tornadoes. G

159/2002 5 Michael Tjernström Professor Department of Meteorology Stockholm University Sweden

Eric Erixon Technician Swedish Polar Research Secretariat

The Meteorological Department of Stockholm University sailed north for the Arctic Ocean 2001 Expedition

The Swedish Polar Research Secretariat carried out a two-month expedition to the high Arc- tic in summer 2001. The Secretariat cooperated with the Swedish Maritime Administration and the icebreaker Oden, which functioned as the research platform. The expedition was participated in by some 50 researchers and Figure 1. Container housing the Vaisala equipment and had several research programs, which dealt the ship’s weather station on the 7th deck of Oden with biogeochemistry, physical oceanography, geophysics, and atmospheric processes. The atmospheric research included a large program of meteorological measurements where several Vaisala products, including sounding systems, radiosondes, heated cup anemometers and other measurement instruments, were used.

he marine Arctic is inti- their history, is essential to pre- mately connected with dict future developments. T the global climate and Swedish researchers have been large-scale biogeochemical cy- active in marine Arctic research, cles. Disturbances and variations with several expeditions carried in the function of these systems out in the 1990s under the aus- can drastically change condi- pices of the Swedish Polar Re- tions of life in countries in the search Secretariat. During the Northern Hemisphere. Under- Arctic Ocean 2001 expedition, standing the natural processes in four extensive international and the Arctic today, and studying interdisciplinary research ➤

6 159/2002 Figure 3. A view of the ice camp taken from Oden’s 7th and highest deck. In the foreground one can see the red huts housing the tethered sounding and Sodar equipment -– the Sodar antennas are the three white cubes. Further away are the 18-m mast and the blue hut which houses the electronics for the mast instrumentation.

Figure 2. The expedition on the icebreaker Oden set out from Stockholm on June 26, 2001 via Gothenburg to the Arctic Ocean, ending at Longyearbyen, Svalbard, on 29 August 2001.

26 June departure from Stockholm, transit and test of equipment 29 June embarking and departure from Gothenburg, transit 4 July leg 1, priority biogeochemical program 14-15 July rotation, change of scientists 16 July leg 2, priority oceanographic program and remote sensing 25 July leg 3, seismology at the Lomonosov Ridge 30 July leg 4, taking of specimens in the Makarov Basin 1 August leg 5, atmospheric research carried out during the ice drift (Oden anchored to drifting sea ice) 29 August embarking Longyearbyen, Svalbard

159/2002 7 Figure 4. The icebreaker Oden functioned as the research platform.

Figure 5. Eric Erixon, a long-time meteorologist with experience of some 10000 radiosoundings, performed numerous soundings during the expedition, here preparing a Vaisala radiosonde for release on Oden’s helicopter deck.

programs were carried out to program was carried out with the cal Institute (SMHI), sending lenge. Some of the instruments study various aspects of the Arc- ship anchored to drifting sea ice. daily HIRLAM-products over could be disturbed by move- tic environment. The sub-pro- During the 20-day ice drift in satellite telephone email. ments, local pollutants or noise grams were atmospheric process- August data was collected using from the Oden. Consequently, es (including marine biology, gas various methods both aboard Meteorological they were located about 300 me- and aerosol chemistry, aerosol the ship and on the ice. Meteor- measurements ters away from the ship on an ice physics, and meteorology), bio- ological instruments included a as a part of the floe, where micrometeorological geochemistry, geophysics and suite of remote sensing equip- atmospheric program measurements were performed oceanography, each of which ment with a wind profiler, a The purpose of the meteorolog- with an 18-m telescopic mast, had a dedicated leg of the expe- cloud radar, a scanning radiome- ical measurements was both to the tethered sounding site and dition. ter and a Sodar. In addition, an complement the atmospheric the Sodar. The stability of the ice 18-m tower with profile, turbu- chemistry and aerosol measure- floe aroused some concern, Versatile atmospheric lence and radiation instruments, ments by providing a detailed since August is in the middle of data collected two remote stations with a com- description of processes relevant the melt season. Fortunately, the The Arctic is an especially inter- plete energy balance instrumen- to the mixing of chemical con- large ice floe with dimensions of esting research area for atmos- tation, and a system for tethered stituents and aerosols, and to in- 1.5 by 3 km proved both suffi- pheric studies as it is especially soundings were mounted on the crease the understanding of the ciently thick and stable. Two ad- sensitive to climatic changes. ice. Atmospheric variables were Arctic boundary layer. The strat- ditional turbulence-flux stations Moreover, the Arctic is the only also measured with some 120 ra- egy was to obtain a continuous were also set up remotely, at a region on the Northern Hemi- diosoundings. Every six hours, record of the lower troposphere distance of 5 and 8 km respec- sphere where the air in summer TEMPSHIP messages were sent conditions by continuously tively. Additionally, the expedi- is relatively free of man-made to the Swedish Meteorological monitoring wind and clouds tion was equipped with a small pollutants, which might other- and Hydrological Institute through the lowest kilometer us- helicopter that had aerosol and wise disturb the measurement (SMHI) which forwarded them ing the remote sensing instru- meteorology sensors for making and observation of natural to the international network. ments. Another aim was to make soundings when the weather processes. Additionally, the European Cen- detailed observations of specific permitted. Our very study sub- The atmosphere program of tre for Medium Range Weather atmospheric events at the 3-week ject, the weather, also affected the expedition aimed to increase Forecasts (ECMWF) was inter- ice camp. our operations - a snowstorm knowledge of the impact of ested in the data, since measure- caused a delay of almost two aerosols on the climate and to ments are not frequently per- Challenging research days in setting up the ice camp. study how natural aerosol parti- formed at these latitudes. Weath- environment cles are produced and transport- er forecasts for the expedition To obtain detailed meteorolog- Soundings amidst ice ed in the Arctic atmosphere. The were supplied by the Swedish ical measurements in the harsh About 120 soundings were car- major part of the atmosphere Meteorological and Hydrologi- Arctic environment is a chal- ried out during the expedition of

8 159/2002 Figure 6. The researchers spotted many polar bears around the North Pole, which followed curiously the research efforts of Oden.

which 80 were launched during ing the main pack ice. During The Vaisala sounding station typically just below zero, i.e. at the 3-week ice camp in August. sessions at research stations was located on the 7th deck of the melting point of the ice. The The remainder were carried out soundings were performed every Oden, the top-deck of the ship temperature dropped lower than during shorter research sessions, 6 hours. Additional soundings (Figure 1), while all radiosondes the freezing point of salty water either in open water or in the were also made in connection were launched from Oden’s heli- (around –1.5 ˚C) only a few marginal ice zone, before enter- with research helicopter flights. copter deck (Figure 5). South of times, which can be seen, for ex- 80˚ N, Loran-C was successfully ample, around day 226, and used for wind measurements, even then only to ~ –6 ˚C. Most while for the helicopter-coordi- notable in the temperature nated soundings we used sondes records is the fact that the tem- Aerosols and their effect without wind sensors (PTU-only perature increased from the top radiosondes). For soundings in of boundary layer and upward on climate the high Arctic, GPS sondes for practically the whole period. were used. Only two of all the The warmest temperatures by far erosols are small particles in the air, such as dust, sul- radiosondes released failed, occurred at an altitude of A phur, pollutants or sea salt, which affect the radiation these were due to balloon mal- around 1 km. In fact, a capping balance of the atmosphere both directly and indirectly. The functions. All the Loran-C inversion prevailed most of the particle size and chemical composition of aerosols deter- windsondes gave satisfactory re- time. The solid blue line is the 0- mine how the aerosols affect the atmospheric radiation and sults, even those released north degree isotherm; for quite a sub- thus the temperature. of Svalbard, where an older re- stantial part of the time the tem- Aerosols scatter and absorb solar and infrared radiation ceiver type (MARWIN) was perature above the capping in- in the atmosphere, which is referred to as direct radiative used. North of 88˚ N, using GPS version was well above freezing. forcing. The aerosols also function as cloud condensation for windfinding, we had a suc- The boundary layer was nev- nuclei, vital to the formation of clouds, which also reflect cess rate of approximately 80%. er very stable and the capping in- solar radiation. Aerosols modify the optical properties and Also the other GPS receivers had version seldom touched the sur- lifetime of clouds (known as indirect radiative forcing). periods of poor reception. face. The inversion was most Consequently, aerosols are considered to have had a cool- pronounced on the very few ing effect on the global climate – an opposite effect to that Some findings of the clear days, see around days 220 – of greenhouse gases, which are known to cause global study 223 and 226 – 227. The lowest warming. However, aerosols typically have a short atmos- A composite of temperature and troposphere was very humid pheric lifetime. For this reason, aerosols cannot be regarded humidity for all soundings from through most of the experiment, as an offset to the warming effect of greenhouse gases. G the ice camp is shown in figures but during these periods some- 7 & 9. The temperature was nev- what lower humidity prevailed er very low at the surface, staying above the inversion. With- ➤

159/2002 9 in the boundary layer, however, camp, provided a wealth of data both snow and rain. The bound- relative humidity seldom on the boundary layer in the ary layer remained relatively well dropped below 85% and often high Arctic that will take us years mixed and cloud-capped almost remained > 90%. The boundary to explore fully. A more or less all the time. As a consequence, layer depth (dashed line in Fig- continuous record of the state of the temperatures were surpris- ure 6 and 7) was typically the lower atmosphere was col- ingly mild and the boundary- around 300 – 500 m, tentatively lected with remote sensing layer stability was rather small. analyzed from the potential tem- equipment, and detailed bound- The often-quoted low-level jets perature profile. ary layer measurements were in the wind speed profile were al- Figure 8 shows a composite sampled on an 18-m mast, by so for most part absent. G of the wind speed during the ice two remote flux-stations and camp period. The white and gray with a tethered sounding system 1 Wind speed (ms ) areas in this plot indicate periods using balloons or kites. Vaisala 12 45 when we were unable to measure radiosondes provided a very winds with the GPS sonde. The good record of the time-height 40 winds in the boundary layer variability of the whole tropo- 10 were usually low, below 10 ms1. sphere. These data are unique 35 Winds aloft were also usually since such a record from a loca- low with the exception of a few tion this far north is very un- 8 30 storms with winds reaching 25 common. 25 1 ms . The first major storm, The summer of 2001 seemed 6 which caused difficulties in set- to be different from previous 20 ting up the ice camp, penetrated summers when the Swedish Po- Altitude (km) deeper. Only slight signs of this lar Research Secretariat has con- 4 15 storm can be seen here as we did ducted icebreaker borne atmos- not start using GPS sondes until pheric research in the Arctic. 10 most of the ice camp instrumen- There were no signs at all of the 2 5 tation was available. much-discussed decrease in either ice-cover or ice-thickness. 0 0 Summary On the contrary, we had quite 214 217 220 223 226 229 232 The main feature of the Arctic severe ice conditions. There was Julian date Ocean 2001 expedition’s atmos- also much more synoptic activi- Figure 8. Composite of scalar wind speed during the ice-camp operations. The pheric program, the 3-week ice- ty, with several storms carrying white and gray areas in this plot indicate periods of unavailable wind data.

Temperature (°C) Relative humidity (%) 4 4

3.5 5 3.5 90

3 3 80 0 2.5 2.5 70

2 5 2 60

50 Altitude (km) 1.5 Altitude (km) 1.5 10 1 1 40

0.5 15 0.5 30

0 0 20 214 217 220 223 226 229 232 214 217 220 223 226 229 232 Julian date Julian date Figure 7. Composite of temperature from all soundings during the ice-camp Figure 9. Composite of relative humidity from all soundings during the ice- operations. camp operations.

10 159/2002 Veijo Antikainen, M.Sc. (Physics) Product Manager

Ari Paukkunen, Ph.L. (Physics). Research Manager, Sensors Vaisala Helsinki Finland

Hannu Jauhiainen, M.Sc. (EE) R&D Manager

Measurement Accuracy and Repeatability of Vaisala RS90 Radiosonde

The accuracy of the Vaisala RS90 Radiosonde is based on the improved sensor technology and individual calibration of the radiosondes. High- performance in-house calibration technology was developed to enhance this accuracy. In this article, the accuracy of pressure, temperature, relative humidity measurements and total uncertainties are discussed.

his article summarizes ly calibrated with sensor elec- diameter of only 0.1 mm. More- ity sensor in comparison to that the paper (Paukkunen et tronics. The calibration equip- over, the response time of the of RS80 is presented in Fig. 3. T al 2001) presented at the ment measures the output data RS90 temperature sensor has Possible condensation of wa- AMS 2001 conference, focusing of the radiosonde sensors in de- been reduced to less than one ter vapor when emerging from a on accuracy and repeatability. fined environmental conditions tenth of the RS80 response time cloud is eliminated through the Please note that some details on and then computes individual (0.2 s vs. 2.5 s at 1000 hPa, 6m/s, use of two heated humidity sen- the measurement and calibra- calibration coefficients for each see Fig.1). The solar radiation sors. As a result, in most cases tion accuracy and repeatability sensor. Ground equipment uses correction has also been reduced where condensation could hap- of RS90 Radiosonde have been these coefficients during sound- remarkably: the correction of pen, the RS90 humidity sensor updated. The Vaisala RS90 Ra- ing to calculate accurate meas- RS90 is about 1/5 of that of performs correctly. diosonde participated in the urement values from the sensor RS80 (Fig. 2). Possible contaminating gas- WMO International Radiosonde output data transmitted by the es reaching the sensor from or- Intercomparison in Brazil in radiosonde. Humidity ganic materials in the ra- 2001, the results of which will be Vaisala’s CAL4 Calibration Wide-range factory calibration diosonde can be eliminated by reported later. Machine was specially designed against well-defined references performing a sensor regenera- for calibrating the advanced has lowered production variabili- tion (heating) procedure before Performance RS90 radiosonde sensors. The ty with the RS90 Radiosonde the factory calibration and dur- characteristics of the new calibration technique also (Table 1). This has also further im- ing the ground check procedure RS90 further improved the accuracy proved sounding accuracy. just before a sounding. With this and reliability of Vaisala’s cali- In radiosonde humidity procedure, the original highly Factory calibration of RS90 bration procedures. measurements, the following accurate calibration of the sen- Calibration and sensor quality factors require special considera- sor is recovered for optimum play a key role in the perform- Temperature tion: performance. ance of radiosondes. For opti- In the construction of the ra- • response time Algorithms for solar radia- mum accuracy, all Vaisala radiosonde temperature sensor the • solar radiation tion correction of the RS90 hu- diosonde sensors are individual- most important design criteria • correction of sensor tempera- midity measurement are current- was to minimize the ture dependence ly under development. The algo- time lag and the ef- • elimination of possible rithms for eliminating the tem- fects of solar and in- condensation of water vapor perature dependence error in frared radiation. To when emerging from a cloud cold temperatures have been im- meet these require- • elimination of possible proved in comparison with the ments the sensor contaminating gases from the RS80 (Balagurov et al. 1998, had to be as small as radiosonde materials. Miloshevich et al. 2000, Wang et possible. The size of al, to be published). Details will the RS90 tempera- The minimized sensor allows be available later in the report ture sensor com- improved humidity measure- from the WMO International plies with this re- ment performance. The re- Radiosonde Intercomparison Figure 1. Response time (63.2%) of the RS90 quirement, with a sponse time of the RS90 humid- 2001. temperature measurement. Averaged over T-range.

159/2002 11 Pressure with the result of a measure- Estimated short and The RS90 incorporates a silicon ment, that characterizes the dis- long-term uncertainty micro-mechanical pressure sen- persion of the values that could values of CAL4 calibra- sor which solves the problems of reasonably be attributed to the tion at various calibra- temperature dependence during measurand. The parameter may tion points at a 2 sigma fast temperature changes and im- be, for example, a standard devi- confidence level are pre- proves mechanical strength duration. Uncertainty gives a cer- sented in Table 1. ing transportation and against tain confidence in the result of a In the calibration pro- other mechanical shocks. measurement. cedure there are also ra- The excellent performance of Repeatability is the close- diosonde-based uncertain- the RS90 pressure sensor during ness of the agreement between ties ( s) from such factors rapid temperature changes is illus- the result of successive measure- as curve fitting, electronic trated in Fig 4. The test was per- ments of the same measurand noise, and resolution. formed in extreme conditions carried out under the same con- Uncertainty estimat- with rapid temperature changes ditions of measurement. Re- ed as the standard devia- Figure 3. Response time of the RS90 humidity from 25ºC to -55ºC and back. In peatability can be expressed tion of differences in re- measurement. Sample size 20 pcs. actual soundings, the maximum quantitatively in terms of the peated calibration ( rc) change is few hectopascals in dispersion characteristic of the includes uncertainties ( r) and urement reference ( m ) and av- RS80 and negligible in the RS90 results (standard deviation). ( s). This means that: erage value (xm) are calculated compared to the RS80. Reproducibility is closeness from a sample inspection of (1) √( )2+( )2 The new calibration facility of the agreement between the re- rc r s RS90 production. This measure- with accurate temperature de- sult of successive measurements The measured values for ( rc) are ment system has its own uncer- pendence correction has im- of the same measurand carried given in Table 2. tainty ( ar). The measured differ- proved measurement accuracy. out under changed conditions of Long-term uncertainty is re- ences are related to t, ar, s, measurement. It can be ex- lated to systematic errors. The and they can be summed up as RS90 uncertainty pressed quantitatively in terms uncertainty is calculated accord- squares of the deviations: estimation in soundings of the dispersion characteristic ing to (I.O.S. 1993; EARL 1997). (3) 2 2 2 of the results (standard devia- xm+3m 3√(t) +(ar) +(s) Definition of accuracy tion). Calibration uncertainty xm—3m When discussing accuracy, it is Calibration is a set of opera- The calibration uncertainty of important to agree on its definitions that establish, under speci- the CAL4 Calibration Machine ( t) can be estimated as ( t2) if tion. Based on the definitions of fied conditions, the relationship is the main factor in RS90 uncer- the maximum value of (xm ± the International Organization between values of quantities in- tainty estimation in soundings. 3 m) is used of Standardization (I.O.S. 1993), dicated by a measuring instru- If l is added to rc, an ini- (4) 2 2 2 the following definitions are ment or system, and the corre- tial (low) estimate ( t1) of total t2 √(xm/3+m) +(ar) —(s) used in this article: sponding values realized by stan- uncertainty ( t) for an individual Accuracy is the closeness of dards. RS90 radiosonde is reached and the high estimate is now the agreement between the re- The concrete basis for ra- If a specific general-purpose (lab- 2 2 (5) t2 √(xm/3+m) —(ar) sult of a measurement and a true diosonde accuracy is the calibra- (2) √( )2+( )2 value of the measurand (I.O.S. tion procedure, the calibration t1 rc 1 When a radiosonde is as- 1993; EARL 1997). Accuracy is a equipment and the international oratory) measurement system, cending carried by a weather bal- qualitative concept. traceability of the references independently from the CAL4 loon, a new set of uncertainties Uncertainty of measure- used in calibration (Paukkunen Calibration Machine, is used to must be considered. They are ments is a parameter, associated 1998). monitor and specify the uncer- mainly attributable to dynamic The starting tainty of the RS90 Radiosonde, measurement or new phenome- point for the estima- a standard deviation of meas- na (compared to CAL4), such as tion of uncertainties ured differences against meas- solar radiation. All these factors in operational radiosoundings are Uncertainty Pressure Temperature Humidity the short-term ( r) hPa °C %RH and long-term ( l) uncertainties of the 0 ... 1070 +60 ... - 90 0 ... 90 calibration equip- Short term 2 ... 1080 0.1 ... 93 ment CAL4. These ( r, k=2) < 0.22 < 0.01 ... 0.03 0.1 ... 0.5 uncertainties arise Long term from such factors as: ( l , k=2) < 0.10 0.05 ... 0.06 0.1 ... 0.6 reference uncertain- Total < 0.24 0.05 ... 0.07 0.2 ... 0.8 ty, conditions in the Table 1. Estimated short-term ( r) and long-term ( l) uncertainty of Figure 2. Solar radiation correction of the RS90 and calibration cham- CAL4 calibration at various calibration points at a 2 RS80. ber. sigma confidence level (95.5%).

12 159/2002 Uncertainty in The standard deviation of Conclusion and factory calibration is the RS90/RS90 difference gives discussion sampled and tested as an estimate for reproducibility The main goals of the RS90 ra- an integral part of of the pressure, temperature, hu- diosonde design were to respond production control. midity and geopotential height to the increasing demand for Additionally, an in- readings (PTUH) of the RS90 in well-defined uncertainties of dependent laboratory soundings. This can be com- measurement and the need for facility is used as part pared to standard deviation of improved repeatability of cali- of the quality control differences in RS90 calibration bration and reproducibility in system. Measure- and specified total uncertainty soundings. Many of the known ment results are used in soundings (Table 2). weaknesses in earlier radiosonde in uncertainty evalu- The RS80/RS90 temperature designs have been corrected. Figure 4. RS90 and RS80 pressure sensor ations mentioned differences are greatly affected by The uncertainty analysis seems responses to fast temperature changes in extreme earlier in this chapter. different types of atmospheric to agree with the uncertainties conditions. The temperature was changed rapidly temperature profiles due to the observed in operational use. from 25°C to - 55°C and back to 25°C. Comparison flight fast response time and small radi- Extensive testing and analy- tests ation correction of the RS90. sis of the radiosonde during op- can be estimated as uncertainty Some of the comparison flight Large differences in height erational use makes it possible to components (I.O.S. 1993; EARL tests were performed as twin or data between the RS90/RS90 further improve the product in 1997) and further combined as triple soundings from 1999-01- and RS90/RS80 values are main- the future. The test facilities for a the sum of squares of deviations 26 to 1999-02-15 at Vaisala ly due to differences in pressure wide range of atmospheric con- ( f). The value of ( t) changes as Helsinki sounding station. A to- sensors and the different re- ditions using high-accuracy a function of several variables tal of 27 soundings were per- sponse times of the temperature methods are being constantly and therefore the expression is formed. The compared ra- sensors. In the troposphere, the improved to reach the best pos- complicated to formulate. If diosonde types were 1 - 2 pcs faster RS90 temperature sensor sible product know-how for our G ( so) is the RS90’s uncertainty of RS90-AL Radiosondes with indicates slightly colder temper- users. calibration, the total uncertainty RS80-15L Radiosonde. The aver- atures. The reproducibility in of the RS90 Radiosonde ( rs) in age of maximum direct differ- test soundings meet the speci- soundings can be estimated as ences and maximum average fied values (in Table 2 the stan- References A. Balagurov, A. Kats, N. Krestyanniko- standard deviations are shown in dard deviation of differences is 2 2 va, WMO Instruments and Observ- (6) rs = √( so) +( f) √ Table 3. divided by 2). ing Methods Report No. 70, Uncertainty ( so) can be esti- WMO/TD No. 877, 1998. European Co-operation for Accreditation mated with t1, t2,for example. Specification P (hPa) T (°C) U (%RH) of Laboratories (EARL): EARL- Further, ( rs) can be compared Uncertainty to the reproducibility of sound- R2,1997. in soundings 1.5 ... 0.7 0.5 5 International Organization for Standard- ings (giving the general variabili- ization (I.O.S.), ISBN 92-67- Reproducibility in 2 ty of sounding measurements). 10188-9, 1993. soundings Miloshevich, L. M., H. Voemel, A. Specifications based on 1080-100 hPa 0.5 Paukkunen, A. J. Heymsfield, S. J. uncertainty evaluations 100-3 hPa 0.3 Oltmans, J. Atmos. Oc. Tech., Feb. On the basis of these uncertain- 2001, Vol. 18, pp. 135-156. 1080-50 hPa 0.2 A. Paukkunen, Veijo Antikainen, Hannu ty evaluations, the following 50-20 hPa 0.3 Jauhiainen, 11th Symposium on specifications can be presented: 20-3 hPa 0.4 Meteorological Observations and In- Repeatability (Standard de- strumentation, 14-19 Jan. 2001, viation of differences between Repeatability 0.4 0.1 2 New Mexico, AMS, 2001 two successive repeated calibra- A. Paukkunen, Vaisala News No. Table 2. Accuracy specifications for RS90. tions, k = 2 confidence level). 147/1998. Uncertainty in sounding (2- Wang J., Cole H. L., Carlson D. J., Miller E. R., Beierle K, Paukkunen A., sigma (95.5%) confidence level P (hPa) T (ºC) U (%RH) H (gpm) Laine T. K., Corrections of Humidity (k=2), cumulative uncertainty RS90/RS90 Measurement Errors from the Vaisala including repeatability, long- Max. average 0.25 0.13 0.50 25 RS80 Radiosonde - Application to term stability, effects due to RS90/RS90 TOGA-COARE Data, accepted to be published in Journal of Atmospher- measuring conditions, dynamic Max. std. dev. 0.40 0.51 0.17 28 ic and Oceanic Technology. effects (such as response time) RS80/RS90 and effects due to measurement Max. average 1.39 0.52 3.6 455 electronics). RS80/RS90 Reproducibility in sound- Max. std. dev. 1.1 0.90 6.0 125 ing (standard deviation of differences, in dual soundings divided Table 3. Maximum direct differences and maximum standard deviations by √2). of test flights (27 soundings).

159/2002 13 David Carlson, Ph.D. Director National Center for Atmospheric Research Atmospheric Technology Division Boulder, Colorado USA

Junhong Wang, Ph.D. Scientist National Center for Atmospheric Research Atmospheric Technology Division Boulder, Colorado USA

NCAR and Vaisala collaboration project for RS80 Humidity Data Set Corrections - Steps to

The Atmospheric Technology Division (ATD) of (e.g. time since the National Center for Atmospheric Research manufacture), obtainable from (NCAR) uses Vaisala radiosondes and drop- the radiosonde sondes to support short-term research projects serial number around the world. Researchers often use the recorded as part ATD data sets long after the initial data collec- of standard data files. ATD and a tion period, and often for purposes beyond few other users the intent of the original project. Likewise, typically record sounding data gathered by various national additional data, weather services as part of their daily opera- especially sensor data before ra- tional observations often become an impor- diosond launch, tant component of longer-term data sets used that, in combi- for reanalysis and climate monitoring. A set of nation with separate surface correction algorithms has been developed in a data, can pro- joint project of NCAR and Vaisala that will vide an alternate support researchers in their work. correction path for sonde humidity bias that he NCAR and Vaisala primary and tractable factors: does not require collaboration project chemical contamination of the knowledge of T started in 1998 and built humidity sensors, temperature sonde age. on a mutual effort to identify dependence of sensor response, The ATD- and correct a dry humidity bias basic calibration models, ground Vaisala correc- in Vaisala radiosondes. Junhong check processes, sensor aging, tion algorithm Figure 1. The cumulative impact of applying the Wang, Harold Cole, David Carl- and solar-induced sensor arm incorporates ATD-Vaisala correction algorithm to the TOGA son, Erik Miller and Kathryn heating. Of these factors, chemi- these various COARE data set. Beierle of NCAR’s Atmospheric cal contamination, primarily factors into an Technology Division (ATD), and from packaging materials, in- orderly correc- Ari Paukkunen and Tapani Laine duces the largest uncertainties at tion sequence with simple input aging corrections, calibration er- of Vaisala have recently pro- warm temperatures and high hu- factors and decision points relat- ror corrections, temperature de- duced a set of correction algo- midities while the temperature- ed to availability of sonde age in- pendence corrections, and sen- rithms that allow researchers to dependence properties of the formation or prelaunch compar- sor arm heating corrections us- reprocess historical sounding da- humidity sensors induce signifi- ison data. Inputs include meas- ing documented assumptions ta sets to obtain improved hu- cant uncertainties at very cold ured humidity, measured tem- and equations at each step. midity measurements. temperatures. The ATD-Vaisala perature, sonde serial number if correction procedures compile recorded and independent sur- Who might use the How do the correction these sometimes offsetting fac- face humidity data if measured, correction algorithms? algorithms work? tors into specific physically- and the algorithms will then pro- Contamination-induced humid- The ATD-Vaisala research on ra- based algorithms for Vaisala A- duce corrected humidity data. ity errors generally increase with diosonde humidity errors identi- type humidity sensors (e.g. Decision points accommodate radiosonde age and with the rel- fied several sensor, calibration, RS80-A) and H-type sensors (e.g. data sets with prelaunch data or ative humidity of the measured and handling factors that can af- RS80-H). In most cases, the cor- which lack sonde age informa- atmosphere. These errors aver- fect humidity measurement ac- rection algorithms for chemical tion. The algorithm applies in age about 2% and about 10% at curacy. The ATD-Vaisala correc- contamination require know- sequence ground check error relative humidities near 100% tion algorithm focuses on six ledge of the radiosonde’s age corrections, contamination and for one-year-old RS80-A and

14 159/2002 er issues of Vaisala News, Vaisala has developed a sensor protection cap on RS80 radiosondes to eliminate chemical contamination. As those protected radiosondes come into wider use and as users evaluate these correction algorithms for more data sets, some of the correction algorithm components might become real-time components of Improved Humidity Measurement data processing systems or standard parts of global reanalyses. RS80-H radiosondes, respective- mate the impact and utility of shows more clearly. Much of the research that pro- ly. Temperature dependence er- applying these algorithms. For many research ques- duced these correction algo- rors occur mainly at tempera- tions, humidity corrections of rithms will apply directly to the tures below -20°C, increase sub- Impact of the this magnitude can have sub- problem of establishing reliable stantially with decreasing tem- corrected data stantial impact. Guichard et al. data continuity as the Vaisala peratures below -30°C, and oc- The efforts of the ATD-Vaisala (2000) showed that corrected user community changes from cur to a larger extent for the team have made the TOGA TOGA COARE soundings re- RS80 to RS90 and newer ra- RS80-A than the RS80-H. The COARE radiosonde data set one sult in the net surface radiative diosondes over the next few ATD-Vaisala correction algo- of the most examined and high- flux increasing by 4 W/m2 under years. G rithm produces substantial hu- est quality radiosonde data sets a clear sky (equivalent to dou-

midity improvements in data ever collected. Figure 1 shows bling CO2). Wang et al. (2001) sets that include measurements the cumulative impact of apply- showed that the use of corrected made in warm moist conditions, ing the ATD-Vaisala correction data enabled some of the first re- such as tropical lower tropo- algorithm to the TOGA liable estimates of long-term he Tropical Ocean Global sphere data sets, or measure- COARE data set. After correc- changes in upper tropospheric T Atmosphere Coupled ments made at cold tempera- tion, over an important air-sea water vapor concentrations. Ocean-Atmosphere Research tures such as in the upper tropo- interaction region as large as the Johnson and Ciesielski (2000) Experiment, TOGA COARE, sphere and lower stratosphere. continental US, surface, mid- show substantial changes in col- was conducted in 1992 and However, because the cor- layer, and upper level moisture umn and volume moisture 1993. It represented one of the rection methods introduce their profiles have all changed. High budgets induced by the correc- largest international research own uncertainties and may not near-surface humidity values tions applied to the TOGA programs of the past twenty- correct all errors in Vaisala RS80 now extend from 5ºN to 5ºS. COARE data. Interested readers five years. More than twenty Radiosonde humidity data, Mid-level moisture values have should consider the published nations provided resources prospective users should careful- also increased while the dry in- description of the correction al- and staff to study the interac- ly evaluate the humidity accura- trusions at 700 mb show in gorithms (Wang et al. 2002) and tion between ocean and at- cy needed, the probable sources sharper detail. Above 300 mb, the various papers reporting ini- mosphere in the western Pacif- of error, and the impact of the moisture levels have increased tial results of using the algo- ic Ocean. G correction changes. An error by more than 5% (due primarily rithms. analysis summary table included to temperature dependence cor- in the published description of rections) and the presence of dri- What comes next? the ATD-Vaisala correction algo- er subtropical air in both north- Based on the Vaisala-ATD re- References rithm allows researchers to esti- ern and southern hemispheres search reported here and in earli- Guichard, F., D. Parsons, and E. Miller, 2000: Thermodynamical and radiative impact of the correction of sounding humidity bias in the tropics. J. Cli- Figure 2. The mate, 13, 3611-3624. TOGA COARE Johnson, R. H., and P. E. Ciesielski, 2000: study required Rainfall and radiative heating from upgraded or TOGA COARE atmospheric budg- enhanced ets. J. Atmos. Sci., 57, 1497-1514. radiosonde Wang, J., H. L. Cole, and D. J. Carlson, operations at more 2001: Water vapor variability in the than forty sites in tropical western Pacific from 20- year the tropical radiosonde data. Adv. in Atmos. Sci., western Pacific 18, 752-766. region. Wang, J., H. L. Cole, D. J. Carlson, E. R. Miller, K. Beierle, A. Paukkunen, and T. K. Laine, 2002: Corrections of humidity measurement errors from the Vaisala RS80 radiosonde - Applica- tion to TOGA COARE data. J. At- mos. Oceanic Technol., in press.

159/2002 15 used overland in applications where only thermodynamic data is required, or is an essential component. Test range meteorology is one example. When Rock- etsonde data is integrated with wind data generated by another source such as a wind profiler, it becomes possible to model pro- jectile trajectories over a wide range of atmospheric conditions. The RK91 can be prepared for launch in less than 10 minutes; it reaches apogee in less than 20 seconds; and provides a detailed thermodynamic profile with 1-sec resolution. After ejec- tion of the sonde payload, the sonde floats to the surface from an average altitude of 1 km in The Vaisala RK91 Low-Altitude Rocketsonde offers detailed boundary layer profiles of atmospheric pressure, less than six minutes. The pres- temperature and relative humidity. sure, temperature and relative humidity sensors used in the RK91 are the same as those used in Vaisala’s RS90 radiosonde. The sensor outputs and sonde- specific calibration coefficients Vaisala Launches are transmitted over the 400.15 - 406 MHz meteorological band to a Vaisala receiving ground sta- the RK91 Rocketsonde tion. The ground station uses the sonde-specific calibration coefficients to convert the sen- Historically, in-situ measurements of pressure, temperature and hu- sor outputs into raw PTU data midity in the boundary layer have required the use of free-flight ra- and outputs it in ASCII text on diosonde or tethered balloon type atmospheric sounding systems. In an RS-232 port. The raw PTU some cases, the use of these conventional sounding techniques is not data is the final product, unaf- fected by filtering, averaging or practical. Where availability of helium or hydrogen is a problem, or other post-processing. when ease and speed of deployment is desirable, Vaisala’s new RK91 Wherever detailed boundary Rocketsonde is an ideal alternative for the acquisition of boundary layer profiles of atmospheric layer profiles. pressure, temperature and relative humidity are needed, the Vaisala RK91 Low Altitude he Rocketsonde, essen- refractivity conditions affecting ed profile down to the surface of Rocketsonde is a practical solu- tially a rocket-deployed the performance of radar and the sea. Data acquired very near tion that is available today. G T dropsonde, was original- microwave communication. the water’s surface is essential for ly designed in co-operation with The Rocketsonde has a key determining ducting conditions. Rocketsonde sounding Johns Hopkins University – Ap- advantage over radiosondes, With a Rocketsonde, vertical component requirements: plied Physics Laboratory, to when acquiring refractivity pro- resolution is dependent on the meet naval shipboard require- files. Data from a ship-launched rate of parachute aided descent • RK91 Low Altitude ments for data used in modified radiosonde is contaminated by (typically 3 m/s with the RK91), Rocketsonde refractive index calculations. the microenvironment sur- rate of data transmission (ap- • Rocket motor Radar performance may be de- rounding the ship, and typically proximately 1 Hz) and humidity • Rocket motor igniter graded in certain atmospheric is not transmitting “clean” data sensor response time. The re- • Ignition Control Unit (ICU) conditions that produce ducting at less than 200 or 300 meters of sponse time is dependent on the • Launcher effects near the ocean’s surface. altitude. The Rocketsonde ejects ambient temperature. When it is • 400 MHz Antenna Good, vertical resolution of pres- its sensor payload outside of the above freezing, vertical resolu- • Antenna pre-amplifier sure, temperature and humidity ship’s microenvironment and tion will typically be 3 meters. • Vaisala Sounding Processor data is essential to determine the thus provides an uncontaminat- The Rocketsonde can also be

16 159/2002 Reijo Miettinen, Senior Lieutenant Leader of the Niinisalo Meteorological Observation Station Reconnaissance Artillery Battalion Artillery Brigade The Finnish Defense Forces Niinisalo Finland The Finnish Defense Forces decided to acquire 10 systems of this kind and these were delivered between December 1998 and November 1999. As is often the case in this kind of extensive system delivery, some mechani- Mobility and ease of use cal solutions naturally needed review by Vaisala after the delivery had taken place. However, Development of the Light Vaisala resolved these issues promptly. In August 2001 the Artillery Meteorological Sounding Brigade trained system users in the Field Artillery from other sites. After the training period, System M200 some of the systems were then handed over to the Readiness The Finnish Defense Forces at the Luonetjärvi Sounding Station in Brigades. Various visiting foreign central Finland pilot tested a Vaisala Radiotheodolite prototype in defense forces have shown great the summer of 1992. Since then a number of development efforts interest in this concept, which is in our opinion the fastest and have been made to develop a truly mobile and compact sounding most compact mobile sounding station which has all of its components integrated on a trailer which system in the world. G is easy to transport and deploy.

he Radiotheodolite Finnish field conditions around trailer, a problem we solved by Main features measurement principle the year. I’m sure that all of mounting removable storage T and its accuracy were Vaisala’s personnel who were in- and transportation boxes on the he light upper air sound- tested through the carrying out volved will remember the condi- trailer. To operate the system the T ing system M200 is an au- of dozens of soundings. Radio- tions of the darkest and coldest operator simply needed to open tomated meteorological data theodolite was compared with Lapland winter at Rovajärvi. the protective tarpaulin, lower acquisition system to help make the Mobile Automatic Sounding Useful ideas on design details the hydraulic support legs, ele- ballistic calculations for field ar- Station (MAMS) and with the and accessories came up, many vate the antenna to the upright tillery and other tactical appli- fixed Omega-based system. of which have been implement- position and prepare the sound- cations. The system is highly au- MAMS Sounding System com- ed in the product. ing computer MARWIN. tomated, including data quality prises a parabolic tracking anten- The removable boxes and control, message formatting na on quite a heavy shelter with New concepts for the Radiotheodolite antenna and distribution to modern a dedicated Sounding Processor. improved performance make the system flexible to use forms of communication. The test results and experience We tested the Radiotheodolite in both mobile and fixed mode. The Radiotheodolite anten- indicated this new concept to be antenna’s various lifting mecha- It is possible to remove the na automatically tracks the a good choice for a light sound- nisms (lifting heights ranged whole Radiotheodolite antenna, movements of the radiosonde. ing system. from a few meters up to 7 me- MARWIN Sounding Processor The sounding system receives The production prototype of ters). Additionally, the basic and power supply boxes from upper air pressure, tempera- the Vaisala Radiotheodolite was concept was to have all needed the trailer for operation in a tent ture and humidity data from tested at the Field Artillery components installed on a light or building. the radiosonde. Wind velocity and direction are calculated

shooting range at Rovajärvi, Lap- SA PHOTO PHOTO COURTESY: land in 1993. The design from the antenna’s elevation demonstrated at the camp intro- and azimuth data and the hy- duced the functionality and fea- drostatic altitude. The system tures which are included in the weighs a maximum of 1300 kg production models. We appreci- (including all accessories) and is ated for instance the system’s towed with a 4-wheel drive ve- light weight and 24 VDC operat- hicle. The trailer houses a hy- ing voltage. Since then Vaisala drogen cylinder, hydrogen gen- has participated in a number of A team of three operators erator, engineering tools, field training camps in Lapland in or- can set up and make the computer, and manual weather der to evaluate the performance preliminary preparations measurement devices. G of the Radiotheodolite in for sounding quite quickly (in less than 7-8 minutes).

159/2002 17 Selwyn Alpert North American Sales Manager Surface Meteorology The 2002 Salt Lake City Winter Olympic and Vaisala Inc Paralympic Games are now a fond memory Woburn, Massachusetts USA of athletic achievement and enjoyable spectator experience. A key aspect of the overall success was the extensive planning and effective implementation of a variety of support activities, including aviation security operations. The USAF Tactical Mete- orological Observing System (TMOS), supplied by Vaisala, provided sports venue real-time meteorological data and played an important role for the USAF to effectively carry out their aviation support activities.

Support for medical and security aviation operations US Air Force TMOS (TACMET) at 2002 Winter Olympics in Salt Lake City PHOTO COURTESY BY UTAH TRAVEL COUNCIL The Salt Lake City • Utah Olympic Park – Bob- Olympic Scene sleigh, Luge, Ski Jumping, Nordic Combined (32 miles east The recent 2002 Winter Olym- from downtown SLC) pics Games and the subsequent • Park City/Deer Valley – Paralympic Games in Salt Lake Alpine Giant Slalom, Snow- City, Utah, during February and board, Freestyle (8 miles further March are now a pleasant memo- from Olympic Park) ry. The Salt Lake Olympic Orga- • Heber City/Soldier Hollow – nizing Committee (SLOC) Biathlon, Cross-Country Skiing, earned high praise in doing a Nordic Combined (15 miles fur- great job in orchestrating all of ther from Park City) the support activities for a record • Provo – Ice Hockey (46 miles number of events during the south of downtown SLC) Games. • West Valley/Kearns – Ice The sprawl of Olympic activ- Hockey, Speed Skating ities was large. In addition to Salt • Salt Lake City – Figure Skat- Lake City (SLC) being the site ing, Short-Track Speedskating for the Opening and Closing ceremonies, as well as Medal Award The Weather ceremonies, there were seven Monitoring Challenge sports venues scattered north Weather information was essen- and south along the nearby tial for the planning and main- Wasach Mountain Range: taining of activities at the Olym- • Ogden/Snowbasin Area – pic Games in SLC and sur- Curling and Alpine Downhill rounding areas. The venues of (51 miles north of downtown the Games spanned a large area SLC) in northern Utah, where the ter-

18 159/2002 TMOS being installed at Mountain Airport. Note mobile ATC Tower on TMOS at Utah Winter Olympic Park site. TMOS team members providing Humvee in the background. TMOS hard-wired to PC in ATC Tower for checkout during a routine site visit. airport operations. Temperature at the time is -4 °F (-20 °C).

rain is complex. Not only out- cific venues, would call for avia- door sport events but also many tion weather data providing real- other activities were affected by time information at specific sites the weather, such as outdoor cer- of interest. emonies, transportation, park- ing, snow making, emergency USAF Aviation Support and security operations. In addi- and TMOS tion to being prepared for ad- Local aviation operations for the verse, even hazardous weather, Olympics were performed by the organizers and athletes par- the US Air Force (USAF), with ticipating in outdoor events con- coordination provided by their tinuously required accurate and Aviation Security Operations timely weather information. To Center (ASOC) at nearby Hill provide this information, an ex- Air Force Base. The ASOC fore- tensive weather support system casters provided forecasts and was developed, which was man- briefings to the pilots. Heli- aged by the Salt Lake City copters from Hill Air Force Base Olympic Organizing Commit- were utilized for security patrols tee (SLOC). It involved meteo- as well as for potential visits to rologists from government agen- and from the various venues. In cies, private companies and the support of these operations, US- University of Utah. 1 AF weather forecasters from Because of the complex ter- ASOC received forecast infor- rain of Northern Utah and the mation from the US National interaction with weather pattern Weather Service (NWS) Western flows from the Northwest, a se- Region Headquarters. Addition- ries of unique microclimates de- ally, they used real-time aviation velop in the area. Weather at one weather data from deployed US- venue can be quite different AF portable aviation weather sta- from other venues, with differ- tions at the sports venues and ences for such parameters as other key locations. temperature, wind, precipitation and visibility. It is for this reason A compact and that performance of aviation op- portable system erations in key corridors be- These USAF aviation weather tween venues, as well as at spe- stations have the military ➤ Entrance to Snowbasin Ski Area. Site of Alpine Downhill and Super-G.

159/2002 19 Mr. Ed Robinson, AFWA contractor and SLC TMOS Team coordinator, Weather office at Snowbasin, overlooking finish line and scoreboard (outside checks out TMOS at the Snowbasin site using a handheld display. office window). Weather forecaster uses display of weather network information as well as local display from nearby USAF TMOS.

designation of AN/TMQ-53 was that they provided reliable siders TMOS data of high quali- forecaster and the equipment Tactical Meteorological Observ- real-time aviation data from the ty. In addition to its local use at available in the past, the ing System (TMOS), and are venues and other sites, which ASOC, the data was forwarded “AN/TMQ-53 is the best tactical part of the AF inventory in sup- was an important supplement to to the USAF Weather Processing weather equipment that AFWA port of tactical aviation opera- the general model forecast data Distribution System (WPDS) for has fielded in the past 20 years.” tions worldwide. This system is available. The TMOS were de- worldwide distribution. Vaisala is proud to have its prod- supplied by Vaisala, and is a con- ployed at 6 sites: Snowbasin Ski ucts appreciated by key military figured version of Vaisala’s Area (Alpine events), Winter USAF’s Overall organizations, as well as to have MAWS201M TACMET Sys- Sports Olympic Park (Bobsleigh, Experience with TMOS been a part of the global stage of tem. These portable aviation Luge, Ski Jumping), Park City Mr. Ed Robinson has been fol- Olympic competition. G weather stations are compact Mountain Resort (Alpine and lowing the implementation of and quick to deploy. They pro- Snowboard), Soldier Hollow TMOS from its initial stages of Footnotes vide continuous automated data (Biathlon and Cross-Country), qualification to its current de- 1) An excellent article in the February for the following parameters: the Mountain Pass location be- ployment worldwide. He has 2002 Bulletin of the American Mete- orological Society Journal describes wind speed and direction (in- tween Salt Lake City and Park USAF weather forecasting expe- Weather Support Operations for the cluding gusts), air temperature, City, and the Mountain Airport rience, and has been the point- 2002 Salt Lake City Winter Games. relative humidity, barometric location. With the TMOS, heli- of-contact from AFWA to the pressure, liquid precipitation, copter pilots and others would end-users (field people who use 2) A more detailed description of the liquid precipitation equivalent know exactly what weather con- the equipment during tactical system is provided in the 2001 Vaisala for snow, visibility, cloud height, ditions were at the specific operations). Mr. Robinson and News article: “Versatile Automated Weather Observation for Demanding precipitation type (present TMOS sites. Based on a very his colleagues at AFWA are Military Needs,” by Hannu Kokko. weather) and lightning detec- positive past experience with the pleased with the very positive re- tion, giving range/direction. TMOS, ASOC felt confident ception the TMOS has received The aviation data is viewed TMOS would be a reliable and from the end-users, including References on a PC (radio or hardwire link) useful tool. And it was! ASOC. Reports back from the 1. Weather Support for the 2002 Winter with MIDAS IV software, pro- The use of the TMOS at the field by combat weather person- Olympic and Paralympic Games. By J. Horel et al. – Bulletin of the Ameri- viding real-time data as well as Olympics was coordinated by nel involved with the deploy- can Meteorological Society: Vol. 83, METAR/SPECI reporting. A Mr. Ed Robinson, a contractor ment and use of TMOS include pp. 227 – 240. handheld display also provides to the Air Force Weather Agency statements such as: “The hand- 2. Versatile Automated Weather Observa- data/diagnostic information for (AFWA) and a former Air Force held display was easy to program tions for Demanding Tactical Mili- a direct readout at the weather man. He and members of his and worked flawlessly, as did the tary Needs. By Hannu Kokko. – station. 2 TMOS Support Team per- MIDAS IV software. The sensor Vaisala News: Vol 155/2001, pp. 14 – 17. formed the installations and in- integration is outstanding.” Ed Real-time aviation data sured information flow made it has indicated that, based on his The value of TMOS to ASOC back to ASOC. The USAF con- experience as a USAF weather

20 159/2002 Hannu Kokko, B.Sc. (Eng.) Product Manager Surface Weather Division Vaisala Helsinki Finland

MAWS Automatic Weather Stations Enhanced with New Features The Vaisala MAWS301 Automatic Weather Station, which was launched last year, has gained a significant market share in the automation of synoptic and climatological networks in Europe and South America. We are now introducing a number of new and enhanced features to the popular Vaisala MAWS product family of automatic weather stations. In line with Vaisala’s commitment to continuous product development, the new features further enhance the use of the MAWS product family.

vailable for both fixed sunshine, rain duration and fuel The Vaisala MAWS family of versatile installations and moisture sensors. Generic sensor A portable use, MAWS interfaces are also now available, Automatic Weather Stations weather stations provide contin- allowing the connection of oth- uous and reliable data on a mul- er, third-party sensors to the he Vaisala MAWS101 Automatic Weather Station (AWS) titude of meteorological and hy- MAWS. T is a compact, economical solution for applications that drological parameters. The The QFM101 Fuel Moisture require accurate and reliable weather data from a limited MAWS product family is used in and Temperature Sensor meas- number of parameters. It is easy to set up and operate. a wide variety of applications, ures the moisture content of ma- The Vaisala MAWS201 Automatic Weather Station is a such as climatological measure- terial on the floor of a forest or truly portable AWS specially designed for temporary instal- ments, hydrometeorological net- other natural area to help forest lations. Its light weight, low power consumption and large works and a variety of research managers assess the danger of memory capacity make it ideal for research applications. and synoptic applications. fire. The QFM101 sensor applies The Vaisala MAWS201M Tactical Meteorological Obser- the carefully selected pine dowel vation System (TACMET) is a compact weather station offer- Extended sensor library to take moisture from the forest ing a broad range of sensors. It is easily deployed in the field The sensor library has been ex- floor and then measures the and offers complete aviation support and lightning detec- tended with new sensors such as moisture content of the ➤ tion. Its modularity makes it easy to up- grade in the field in support of different tactical missions. The MAWS201M TACMET is the meteorological system used by the US Air Force in their AN/TMQ-53 (TMOS) system. The MAWS301 Automatic Weather Station is designed for applications where commercial power and communications networks are not available. An extensive library of sensor and The MAWS product family is telemetry options makes the MAWS301 used in a wide variety of the ideal choice when a wide range of applications, such as climatological accurate meteorological and hydrome- measurements, research, precipitation networks, energy teorological measurements are re- production and management, and quired with a low ownership cost. G building automation.

159/2002 21 wood according to its electrical QSE101, can also be selected capacitance. In addition, a ther- from the sensor library. mistor located in the dowel measures the temperature of the Serial communication forest floor. Many of the new sensors have The QMT107 Multi-level their own microprocessor and Soil Temperature Probe is a fieldbus for data transmission. unique sensor measuring air/sur- To make sure that these new sen- face-soil temperatures at 7 differ- sors can be interfaced with the ent levels. The sensor probe is MAWS, the DSI486 Dual Isolat- buried into the soil using a speed RS-485 Communication cial auger. The sensor levels have Module has been added as an been selected so that they corre- option. This module offers two spond to the WMO instructions isolated RS-485 I/O lines for in- (WMO book No. 8), with addi- terfacing sensors and/or displays tional sensors at ground level to the MAWS System. Alterna- and 5 cm above it. The sensor el- tively, the same module can be ements are accurate Pt-100 resis- configured by the user to have The generic sensor interface allows the user to set up powering, conversion and tors (IEC 751 1/3 Class B). As one RS-485 and one RS-232 data validation parameters. well as being a very compact sen- port. Moreover, there is a SDI- sor, the QMT107 takes only one 12 port for interfacing hydrolog- differential sensor input in the ical sensors, for example. mission. The first systems using power in a system powered by a logger. The command set in- this geostationary satellite sys- solar panel. cludes a single-point calibration Telemetry tem are now operational in command for calibrating all sev- When monitoring remote sites, Brazil. The Brazilian AUTO- Statistical calculations en sensors at the same time in a telemetry plays a most signifi- TRAC system delivers the data The MAWS System automatical- waterbed at the same tempera- cant role. Telemetry often makes 100 % reliably and in real-time. ly calculates statistical parame- ture. up the most significant part of The data are received with a de- ters such as average, minimum, For water-level measurement the annual operating cost of a lay of only 2-9 seconds in the maximum, standard deviation there are now several alternative monitoring network. Therefore, ground receiving station’s server. and sums, over periods and at methods which can be selected in the MAWS Systems we have The data is available for the user intervals that the user can speci- depending on the characteristics paid special attention to teleme- at any time, for instance if there fy. This feature has been expand- of the installation site and exist- try options. The wide range of are no preset time windows de- ed to allow the reporting of the ing structures. As an addition to telemetry options has been fur- fined by the satellite operator. intermediate values of these cal- the current methods of pressure ther enhanced with the possibil- The MAWS has the means culations. For instance if we sensor and ultrasonic sensor, an ity to use the OmniSAT satellite to switch on and off the trans- have a standard calculation of Incremental Shaft Encoder, system for real-time data transmitter automatically to save hourly averages for air temperature, reports of 10-minute values will also be available (average, The QMT107 Multi-level Soil Temperature Probe measures air and surface soil minimum and maximum) for 0 - temperatures at 7 different levels. 10, 10 - 20, 20 - 30, etc. minutes. Data logging Data logging can be done by logging user-defined data groups at freely configurable intervals. Logging can also be triggered by a measured or calculated parameter exceeding the user-set threshold value, in other words an alarm. The internal flash memory of 1.7 Mbytes is sufficient for most applications. However, for extended memory requirements, there is a Com- pact flash memory card option, which enables the logging of New serial communication modules allow flexible sensor hundreds of megabytes into interfacing. standard CF cards.

22 159/2002 The memory capacity of for example, only every 3 or 6 tion devices and wiring terminals the QML102 AWS hours. for whenever larger systems must Logger can be extended The user also has the option be engineered. with a Compact flash of compressing the report(s). The new design also includes memory card. This function is particularly use- a white painted back plate as ful when the data is transferred standard, and new brackets for using methods which are costly mounting the enclosure to pole or otherwise limit the amount of masts of various diameters. data to be transferred. Such methods include, for example, New tiltable mast satellite systems and SMS (Short To install a 10-meter mast or Message Service) messages in maintain wind sensors at that cellular data transfer. height has previously required 2 There are two methods for - 3 people. The new tiltable mast automatic report formatting: DKP210 can be installed or low- BASE32 and BCD. The ered by just one person, which BASE32 formatting method significantly reduces the annual produces ASCII data and thus maintenance cost. Installation printable characters. In this has also been made easier with method, every data item on the the careful design of equipment report is scaled and converted mounting hardware and a lighter using a radix of 32 instead of the weight. Special attention has normal 10. The BCD (Binary been paid to proper lightning Coded Decimal) method is a Po- protection and grounding of the sitional Number System, with a mast. The mast includes one set radix of 10 and coefficients ex- of guy wires, a lightning rod and pressed in a 4-bit binary word. a complete foundation set for The BCD formatting method new or old concrete blocks. An produces non-printable binary extra set of guy wires and a Report formatting the logged data items are organ- reports. winch, which can easily be in- ized in columns, in such a way stalled and carried, are also avail- When the user configures the that one column consists of the Flexible mechanical able as options. output reports, a very user- measurements of one item over design friendly interface provides access a user-set period of records. In The MAWS301 System includes Versatility for various to all the MAWS’s measured the CHANNEL ordered report a large number of telemetry and applications and calculated parameters. This format, the logged data are or- powering options. In addition, Configuration of the MAWS feature has been further en- ganized in rows, with one row some of the new sensors require System is flexible and the system hanced with new options. consisting of the measurements new powering arrangements, can incorporate a large number The logged data can also of one item over a period of such as, for example, the heated of sensors and telemetry options, now be automatically formatted records. The data items are, by ultrasonic anemometer. There- all of which are easy to install. as reports. The user can select default, separated by a space, but fore the layout of the system These features make the MAWS the number of records from the the user can also change this components in the equipment System a cost-effective and reli- logged file to be included in the parameter. enclosure BOX501 has been re- able choice for a vast number of report. There are two automati- This option is the most con- arranged to allow easier access to meteorological and hydrometeo- cally made report formats. venient when data is not needed them. There is also now more rological monitoring applica- When using the SCAN format, in near-real-time but will be sent, space for optional surge protec- tions. G

The new tiltable mast facilitates easy installation and maintenance.

159/2002 23 IMGW representatives participated in the Factory Acceptance Test and product training at Vaisala. From the left: Mr. Andrzej Maciazek, Chief Engineer, Mr. Jan Orlowski, Chief of the Teleinformatic Center, Beata Surdyk, Practicant, Piotr Pitrzykowski, Engineer, Chief Engineer, Mr. Andrzej Krzysztof Szymanski, Maciazek and Chief of Engineer, Sebastian Teleinformatic Center Mr. Jan Modliszewski, Orlowski testing the MetMan Engineer. Observation Console.

Fifty MAWS Automatic Weather Stations to Synoptic Stations in Poland

ccording to the con- The delivery includes 50 tains full SYNOP and other tract signed in late Vaisala MAWS301 Automatic weather message support. A 2001, Vaisala will sup- Weather Stations, with sensors Vaisala has delivered some ply fifty Automatic Weather Sta- for measuring wind, pressure, air 120 MAWS stations to Poland in tions to the Polish Institute of and soil temperature, relative total, about 50 of which are used Meteorology and Water Manage- humidity, solar radiation, pres- as climatological stations by ment (IMGW). Delivery and in- ent weather, visibility and cloud IMGW, whereas the current de- stallation will take place in 2002. height. The delivery also in- livery is meant for the synopti- The Factory Acceptance Test was cludes an Observation Console cal stations of IMGW. The re- successfully passed in April 2002. (MetMan) for collecting and mainder are used in applied me- The project is financed with a managing the measurement da- teorology. G World Bank loan. ta. The MetMan Console con-

24 159/2002 Traditionally, transmissometers have been the at Vaisala’s outdoor test field, established type of visibility sensor for runway along with reference transmis- visual range (RVR) measurement, a key safety someters and other instrumentation. The FS11 offers a measure- parameter in commercial aviation. In recent ment range of up to 75 km and years, another type, the forward scatter sen- meets WMO, ICAO and FAA sor, has begun to gain acceptance around the specifications for visibility meas- world for this demanding application. The urement in civil aviation. new Vaisala FS11 Visibility Sensor offers a Operates reliably in the number of new features that ensure reliable worst weather visibility measurement in any weather. Four main design features are combined in the FS11 to ensure that it operates reliably in the New technology for runway visual range application harshest weather. The first is the window contamination compensation technique. The second is the “head-down” design FS11 Visibility Sensor of the optical heads, which pro- tects them against virtually all wind-blown particles (even those flying horizontally). High-power Launched heaters are the third feature, each with its own temperature monitoring and control mecha- nism to prevent snow accumula- tion during the heaviest snow- Automatically storm. As a final measure, there compensates for is optical path clearance moni- window contamination toring circuitry to verify that measurement is not affected by Unlike most forward scatter sen- obstructions. sors, the FS11 incorporates a new technique that measures A snap to service and compensates for the attenu- The FS11’s sophisticated self-di- ation effect of window contami- agnostics and modular design al- nation. It ensures that measure- low for very short service times. ment accuracy is maintained The measurement fork and op- throughout the recommended tional background luminance interval between window clean- meter (LM21) are independent ings – and it lengthens this inter- instruments that can be replaced val. The system works by moni- quickly as pre-calibrated spare toring the total reflectance of the parts. window surface. It automatically compensates for visibility meas- New level of reliability urement errors caused by win- in background lumi- dow contamination. nance measurement A new LM21 Background Lumi- A scientifically valid nance Sensor has been launched chain of calibration along with the FS11. The LM21 When evaluating forward scatter provides similar monitoring and sensors, special attention must contamination compensation be paid to calibration. Every features as the FS11, and raises Vaisala FS11 is calibrated background luminance measure- through a scientifically valid ment to a new level of reliability. chain of reference. The scattering Traditionally, background lumi- The Vaisala FS11 Forward response of the calibration de- nance sensors have either incor- Scatter incorporates a new technique that measures and vice can be clearly traced to a ref- porated rudimentary self-moni- compensates for the attenuation erence FS11 Visibility Sensor, toring features or had none at effect of window contamination. which is in continuous operation all. G

159/2002 25 Vaisala LD40 Ceilometer launched such as the laser transmitter can easily be replaced in the field Cloud Height Measurement up to High Cirrus without optical realignment. Due to its measurement The Vaisala LD40 Ceilometer is a compact and When the cloud base is obscured, range, the LD-40 is especially eye-safe ceilometer for cloud detection and by, for example, heavy precipita- suitable for synoptical measure- tion, and it cannot be distin- ment stations where the detec- atmospheric profiling up to a height of 43,000 guished, vertical visibility is still tion of high clouds is also desir- feet (or 13 km). The high measurement range reported. In addition to the stan- able. At the moment, the largest enables the detection of high cirrus clouds not dard data message the LD40 can installed bases are operated by reached by any other standard ceilometer. also report raw measurement da- the German Weather Service ta, which can be utilised for dif- (DWD) and the Royal Nether- ferent research purposes. lands Meteorological Institute he Vaisala LD40 is a long- ceilometer calculates cloud (KNMI) at their weather obser- T range ceilometer for cloud height and evaluates maximum Reliable instrument for vation networks. G detection and atmospheric pro- detection range, vertical visibility versatile use filing that operates up to 43,000 and precipitation intensity sta- The LD40 operates unattended The Vaisala feet (13 km) and offers a vertical tus. under all climatic conditions. In- LD40 resolution of 25 feet (7.5 m). The ternal monitoring ensures reli- Ceilometer measurement principle is based High performance able operation: messages are au- offers a high measure- on the LIDAR technique (Light under all kinds of tomatically transmitted contain- precipitation ment range Detection and Ranging). Short ing information on internal di- enabling the pulses of light are emitted by a The standard report that the agnostics. The LD40 can be op- detection of laser diode, focused to a parallel LD40 produces includes height erated as a stand-alone instru- high cirrus beam, then transmitted vertically values for up to 3 cloud layers. ment or as part of a large mete- clouds. into the atmosphere. Part of the The long measurement range al- orological system. Connection light is scattered back to the lows cirrus clouds to be detected to different systems is, in fact, ceilometer from the aerosols in at a high altitude. Sophisticated very flexible as the data line can the atmosphere (clouds, precipi- algorithms are employed to en- be configured to use different se- tation, fog etc.). From the re- sure reliable cloud detection un- rial interface protocols. Its de- ceived backscatter signal the der all kinds of precipitation. sign is modular: subassemblies

Complete aviation support Romanian Air Force choose Vaisala Aviation Weather Reporter AW11

n Romania a program to devel- The Vaisala Aviation Weather Reporter AW11 installed at Borcea I op a National Integrated Mete- Air Base . From the left product engineer Kusti Kairikko of orological System (SIMIN) is un- Vaisala, captain-commander Dan Florea, Chief of the Air Forces der way. The program has been Meteorological Service and captain-commander Simion Pop of the carried out by Lockheed Martin Romanian Air Force. Overseas in cooperation with the Vaisala TACMET Stations were Romanian National Meteorolog- deployed on the roof of the Free Press ical and Hydrological Institute. In House in Bucharest to support the this framework, two Vaisala Avia- National Day parade. tion Weather Reporter AW11 Systems were installed at Roman- ian Air Force bases in November 2001 and an additional two systems in spring 2002. For the next two years, SIMIN will provide meteorological infrastructure upgrades in Romania, including the integration of ground, altitude, radar and satellite meteorological data, as well as disseminating the data to users in realtime. The Romanian Air Force chose to acquire Aviation Weath-

26 159/2002 At present, Helsinki-Vantaa Airport serves over 10 million PHOTO COURTESYPHOTO FINNAIR BY passengers every year, and has er Reporter AW11 Systems man- been rated as one of the best ufactured by Vaisala on the basis airports in the word in the past of the special qualities, perform- four years. ance and functionalities provided for meteorological support necessary for the training and operations of the Air Force. The Air New runway for larger capacity Force also appreciated the system concept and technology, being also compliant with the NATO Vaisala Equips Helsinki-Vantaa requirements. The fully automatic Vaisala Aviation Reporter AW11 is a stand-alone weather Airport with Automated observation and reporting system which measures all standard avia- Weather Observing System tion weather parameters and gen- erates accurate real-time weather reports. Standard measurements Vaisala has signed a contract with the Civil handle weather data from run- include sky condition (cloud lay- Aviation Administration of Finland to deliver ways 1 and 2. Vaisala is the er height and coverage), visibility, a MIDAS IV Automated Weather Observing prime contractor supplying the air pressure, temperature, dew- aviation weather system to point, and wind speed and direc- System (AWOS) to Helsinki-Vantaa Airport. Helsinki-Vantaa Airport’s Run- tion. Precipitation occurrence Under the terms of the contract, Vaisala will way 3 project. and intensity measurements are deliver an Automated Weather Observing also available.G Leading the way System and associated meteorological This deal marks a significant first sensors to the new runway of the airport. for Vaisala. The Vaisala MIDAS The system will be installed in summer 2002, IV AWOS, which will totally re- TACMET Systems and the new runway is scheduled to open in place Helsinki-Vantaa’s current, at National Day self-designed AWOS, will be in- Parade November 2002. stalled in summer 2002 in prepa- ration for the new runway’s in- he Romanian Air Force he Vaisala MIDAS IV auguration, and will gather and T units participated in Airport Weather Observ- integrate meteorological data the annual parade organ- T ing System (AWOS) will from all 3 runways. Further- ized in Bucharest in cele- gather meteorological data from more, Vaisala will act as the bration of Romanian Na- sensors installed along Helsinki- main weather observation con- tional Day on December 1, Vantaa Airport’s existing two tractor, incorporating an 2001. Among other demon- runways, as well as from the ATIS/VOLMET system provid- strations, a formation of six Vaisala meteorological sensors ed by Terma A/S, a leading Dan- “IAR Socat” - type helicop- that are included in the deal to ish contractor, and control tower ters executed a formation be delivered for the new third displays provided by FRE- flight. runway. QUENTIS Nachrichtentechnik The Romanian Air GmbH of Austria, headquar- Force chose Vaisala’s Tacti- Meteorological sensors tered in Vienna. cal Meteorological (TAC- for the new third MET) Observation System runway New runway increases to support this popular Vaisala sensors for measuring capacity at Helsinki- event because of the ease meteorological parameters, Run- Vantaa Airport of deployment, reliable way Visual Range and cloud Construction of the new runway performance and versatile height will be installed along the (runway 3) at Helsinki-Vantaa measurements. The en- new runway. For ice warnings Airport is one of the major re- hanced configuration of- and predictions, Vaisala will also cent airport developments in fered accurate measure- deliver three ROSA Runway Europe. Scheduled for inaugura- ments of weather parame- Weather Stations, maintenance tion in November 2002, runway ters, such as cloud base, vi- information from which will be 3 will be used as the main run- sibility and wind, which shown on displays incorporated way for takeoffs, allowing some were crucial to support the in the MIDAS IV AWOS. An 40% increase in operations ca- helicopters participating in integrated management system pacity over the current two-run- the parade. G is included in the deal that will way system. G

159/2002 27 Taisto Haavasoja R&D Manager Ville Haavisto, M.Sc. (Eng.) Electronics Engineer Markus J. Turunen, M.Sc (Eng.) Scientist Pauli Nylander, M. Sc (Eng.) Software Engineer Vaisala Helsinki Finland

Yrjö Pilli-Sihvola Head of the Traffic Information Centre Finnish Road Administration Southeastern Traffic Management Centre Figure 1. A picture of the field trial site taken by the road Kouvola weather camera. An arrow marks the DRS511 road sensor. Finland The ROSA Road Weather Station is located outside the view. A Field Trial of Vehicle Grip Compared to RWS Data

Driving safety is a key concern for road authorities. Other than the weather, one of the most interesting factors which affects safety is a vehicle’s grip, i.e. the friction between a vehicle’s tires and the road surface. Together with the Finnish Road Administration Vaisala conducted a field trial in Southern Finland during the winters of 1999-2000 and 2000-2001 to study which measurement results best indicated a vehicle’s grip. In the trial, the measurements from the Vaisala ROSA Road Weather Station (RWS) were compared with independent hu- Figure 2. The average thickness of the ice layer compared to the grip man observations of vehicle grip. observations. It has been determined in laboratory tests 2 that an ice layer of 0.05 mm is the threshold value for dangerously slippery roads.

he use of automatic road on a number of conditions and The trial setup tion site set in demanding weather stations has be- the study focused on researching For the trial, a test system was set weather conditions and it was to T come increasingly com- exactly which measurement re- up with both the latest available yield a wide range of observa- mon to help make road main- sults best indicate a vehicle’s sensor technology and inde- tions on vehicle grip. The road tenance decisions in countries grip. To this end, a field trial was pendent human observation. was also monitored with a road which experience adverse surface conducted using an installed The test was conducted in such a weather camera. weather conditions in winter. road weather station (RWS) to way that there was no feedback The measurements were car- Modern road weather stations find out which of its measure- in either direction. The field test ried out using the Vaisala provide the user with a wide ment results best indicated a ve- was conducted at the Utti road DRS511 Road Sensor 1 and were range of measurement results, hicle’s grip on the roadway. A weather station in Southeastern analysed by the ROSA Road for example road surface temper- total of 530 human observations Finland during the winters of Weather Station. From the wide ature, detailed classification of of grip were collected by 1999-2000 and 2000-2001. The range of output data, the thick- road conditions, thickness of wa- FinnRA during two winters. The Road Weather Station was locat- ness of ice and water were cho- ter and ice on the road, freezing measurement results and obser- ed beside a two-lane main road sen to be used. To get the most point temperature, and amount vations were analysed at Vaisala with average daily traffic of 8700 representative data, the DRS511 and concentration of de-icing both manually and using a neu- vehicles. The test site was a very was located in the wheel track of compound. The grip depends ral network. typical Finnish road weather sta- the lane.

28 159/2002 The human It can clearly be seen that on observations average the grip correlates well The observers for the trial were with the thickness of ice layer. drawn from the staff of the The thicker the ice layer, the Finnish Road Administration. worse the grip. It is also interest- Altogether they collected 530 in- ing to note that very thin ice lay- dependent human observations ers do not necessarily make the of vehicle grip. The observations road slippery: the average thick- were made over two winter ness of ice in the good grip class weather periods from 16 Novem- is 0.02 mm. This is in line with ber 1999 - 28 March 2000 and 9 laboratory tests 2, in which the November 2000 - 28 March effect of ice thickness on grip 2001. The observations were col- was examined in laboratory con- lected at different times of the ditions. There results showed day on almost a daily basis. that an ice layer of 0.02 mm on The observations were col- asphalt does not reduce grip sig- lected by driving past the road nificantly, whereas a layer of weather station amongst other 0.05 mm was found to be the traffic, and therefore represented threshold value for dangerously a typical road user’s impression slippery asphalt. of vehicle grip. The observers The other grip classes also Figure 3. The root mean square deviation of the trained artificial neural were all professionals with exten- correspond with this threshold network with different inputs. The letters (TGHDP) indicate the sive experience in classifying line. The threshold line could be combinations of input data used. winter road conditions. expected to be located some- Grip was divided into three where between the reduced and ROSA shows a thickness of ice ing grip. The data used as input classes: good grip, reduced grip, poor grip classes. However, the greater than 0.05 mm, grip will contained the following quanti- and poor grip. These classes gave threshold line that actually re- be reduced or poor with a sub- ties obtained from the measure- sufficient information on road sulted is likely due to the fact stantial accuracy of 97.4 % of all ments of the road weather sta- conditions and were also suit- that the laboratory tests were observations. tion: able for the observation method. made with a normal piece of tire In the reduced and poor grip • The road surface The following criteria were ap- whereas the observers used stud- classes we find thicknesses as temperature (T). plied: ded tires. high as 2 mm, which is common • The measured amount of when it is snowing. However, 40- de-icing chemical (G), in Table 1. Grip Classes Used in Observations 45 % represent cases where the this case sodium chloride thickness is below the threshold expressed as total amount Grip Class Criterion Number of line but the road is still slippery. per surface area. Observations This differs from the assumption • The combined thickness of Good grip The road is dry, moist, or wet, but not snowy or icy 420 that grip is always dependent on ice and liquid water on the the thickness of ice. Indeed, in roadway (H). This also Reduced grip The road is somewhat icy or most cases snow was packed as a includes snow and possible snowy, but the vehicle is only thin slippery layer on the road hoar frost reduced to their slightly sliding when braking. 86 surface. Thus, even a thin layer of water equivalents. Poor grip The road is entirely icy or ice can actually be slippery. There • The difference between the snowy, and the vehicle is may also be a little salt present surface temperature and the clearly sliding when braking. 24 that is not enough to reduce slip- freezing temperature of the periness. We may conclude that solution on the road (D), Total 530 if the thickness of ice is below and 0.05 mm, grip can be determined • The rate of precipitation (P), The observations can be In summary, the results show to be good with an accuracy of as measured by the road considered as representative data that on average the thickness of 90.6 % of all observations. weather station. as the number of reduced and the ice layer indicates a vehicle’s To find out whether there The input data was then poor grip observations was fairly grip very well. However, to an- were other indicators of vehicle used to train the perceptron with high, altogether 21 %. swer the question whether grip grip beside the thickness of the the observed grip figures as de- can be determined only on the ice layer, we next examined the sired output. The usual back- Results basis of ice thickness in all cases, data with an artificial neural net- propagation algorithm was ap- First we examined the thickness we studied the distribution of work. plied in the training. The root of the ice layer compared to the thickness in each grip class. mean square deviation between observed grip. The results are In the good grip class, 97 % Neural network results the trained perceptron output shown in fig. 2. The three data of cases stay below the threshold An artificial neural network and the observed data is shown points in fig. 2 were calculated line. The remaining 3 % repre- model (multilayer perceptron) in figure 3, when the input data by taking the average value of sent conditions with light snow was fitted into the data in order included in the model was var- the thicknesses of the measured or a thin layer of slush on the to find out which measurements ied in different combinations. A ice layers in each grip class. road. It is thus obvious that if are of importance in determin- smaller deviation means ➤

159/2002 29 Winter Road that the inputs will better ex- he Road Traffic Authori- plain the observations. ty is the State Govern- Congress dealt with Figure 3 shows that when T ment agency responsible New Challenges for the thickness (H) is not included for main roads, motor vehicles Winter Road in the inputs, the deviation is and motor users in New South Maintenance clearly greater. The smallest devi- Wales, Australia. Focusing on ations are obtained in the cases safety concerns, the RTA has de- aisala participated in the when both the thickness (H) and veloped systems to continually V XIth Winter Road Con- some temperature data (T or D) monitor road conditions, using gress 28 - 31 January in Sap- is included. Figure 5. Ville Haavisto of Vaisala hazard detection devices. The re- poro, Japan. Arranged by the presented the vehicle grip survey at al-time information can be dis- World Road Association PIARC Conclusions the SIRWEC conference. played on variable message signs under the theme New Chal- In this study the manual analysis (VMS). For instance, in 1995, a lenges for Winter Road Main- of the data showed that the 12-kilometre network of fibre- tenance, the congress attract- thickness of the ice layer on the ever, to detect only the thickness optic variable message signs was ed a record number of atten- road is the main indicator of ve- is not sufficient in all situations. connected to 10 fog detection dees: 2200 people from 62 hicle grip. The neural network The road weather station should units and 24 speed detection de- countries. analysis also supported this re- also be capable of measuring vices to target individual mo- In conjunction with the sult. When the thickness of the road surface temperature and torists on the appropriate speed Winter Road Congress, the ice layer was greater than 0.05 freezing temperature which were behaviour for the visibility. Standing International Road mm, we could determine with found to be among the best indi- Changeable message signs have Weather Commission (SIRWEC) an accuracy of 97.4 % that the cators of vehicle grip in this set also been provided at several lo- Conference was also held in grip would be reduced or poor. of data and observations. G cations which are connected to Sapporo. Organized every 2 On the other hand, when the presence detectors to advise years, SIRWEC discusses the lat- thickness of the ice layer was be- Acknowledgement drivers when queues build up at est research and technology low 0.05 mm, it was still possible The authors wish to thank Mr. Ossi sites with restricted sight dis- Pilli-Sihvola, Head of the Traffic Infor- concerning roads under a vari- to assess the grip but in some tances. These displays revert to a mation Centre, and also the personnel ety of weather conditions. cases the thickness alone did not of the Road District of Southeastern different message when queues Moreover, this conference also yield enough information. Fur- Finland for their help in conducting are not present. The RTA’s presents meteorological instru- thermore, the neural network this trial and arranging the observa- Southern Region have now ex- ments and related technology. analysis revealed that the second tions. panded the use of these signs to Founded in 1909, the important factor indicating grip provide a changeable sign at a World Road Association (PI- was the difference between road References sub-standard curve location ARC) deals with road infra- temperature and freezing tem- 1. Haavisto, Haavasoja, Turunen, Nylan- where wet weather conditions der: Performance of a Road Surface structure planning, design, perature. significantly increases the hazard Condition Sensor. Proceedings of the construction, maintenance and Based on this data we can 10th International Road Weather to motorists. In wet weather and operation. Its membership in- conclude that it is essential for Conference, 2000. Pages 145-152. when the pavement is wet, the cludes 97 national or federal the road weather station to accu- 2. Nicolas, Jean-Peter: Glättebildung durch advisory warning provided to government members, 2,000 rately measure the thickness of Überfrieren. Schwellwerte der Ober- motorists changes to reflect the collective or individual mem- the ice and water layer in order flächenfeuchte auf Fahrbahnen. Bast increased risk at the site. This ar- bers and over 750 experts in 20 to detect the likely grip and warn Heft V 36, 1996. 26 pages. ticle provides information on standing Technical Commit- about slippery conditions. How- the development of this system tees. and the behavioural response of The Standing Inter- motorists to the changed advice national Road Weather for different conditions as they Commission (SIRWEC) travel through the curve. was originally set up in 1985 as SERWEC (Stand- Site selection ing European Road The Princes Highway is the ma- Weather Commission), jor highway running south, fol- but to reflect changes in lowing the coast. On the Princes the organization’s scope, Highway immediately south of the name was changed in Kiama is a 2.3 km section of 4- 1992. SIRWEC operates as lane road, which is built on a a forum for the exchange winding alignment developed in of information relevant the first half of the last century. to the field of highway The speed limit is 80 km/h. An meteorology, including, accident study shows that in the for example, manage- 3-year period from 1996 to 1998, ment, maintenance, road 65 accidents occurred within the safety, meteorology, and section of which 58 (89 %) were environmental protec- Figure 4. Vaisala showcased road weather products at the PIARC exhibition in wet weather conditions. This tion. G in Sapporo. compares to 65 % of accidents

30 159/2002 Dr Graham Brisbane B.Eng. M.I.E. (Aust), Fellow of the Australian Institute of Traffic Planning and Management

Andrew Vasiliou B.Eng., B.Comp.Sc., M.I.E. (Aust) raining as well as the pavement conditions in terms of dry/moist/wet. The equipment Dynamic warning signs act as is also capable of detecting other conditions such as frost and snow which, however, are not relevant at this site. Details of Signs of Rain the display triggers are shown in table 2. Flashing Lights are at- tached to the sign for use in the A number of systems have been introduced in recent years that third mode, which is assessed as provide dynamic advice to motorists on the real-time status of the most dangerous situation. the road network. Most commonly, motorists obtain real-time In order to assess the effectiveness of the system, speed de- information on congestion, allowing them to take alternate tection loops were placed in routes for reduced travel time. However, the Roads and Traffic both lanes as shown in fig. 3. Authority of New South Wales uses road weather systems and This allowed speeds to be measured during different condi- variable message signs to improve road safety. These systems al- tions. For each vehicle, speeds low drivers to modify their speed behaviour on the basis of were measured together with changes in weather conditions. For instance, information on wet records of lane (fast or slow), conditions is provided for locations where wet weather increases time of day (to assess day and night effects), rainfall and pave- the hazard to motorists. ment conditions. Vehicle lengths were also recorded in order to provide data for heavy ve- curred at the location selected, hicles and motor cycles. No with 10 of those occurring in the changes are proposed to sign- northbound direction. posting for southbound traffic. Site details Effects of signposting The selected site contains a right assessed hand curve on a 4-lane section The site was commissioned on of the Princes Highway separat- 30th May and speed measure- ed by a New Jersey kerb. Annual ments were taken for a period rainfall is in the order of 120 cm, before the sign was activated to and there is an Annual Average assess the effects of traditional Daily Traffic (AADT) in excess signposting. These measure- of 13000 vehicles per day. A ments are to be continued until curve warning sign is currently a behaviour pattern had been es- Figure 1. Selected site. located in the approach to the tablished in wet as well as dry curve with an advisory speed of conditions. At the time of writ- occurring in wet weather in the vision of skid-resistant pave- 65 km/hr. ing the site remains in this con- next homogeneous section of ments at the most frequent acci- In establishing the trial site, dition as insufficient rain peri- the Princes Highway immediate- dent locations. In 2000, New Jer- the sign has been converted to a ods have occurred to allow an ly to the south. sey kerb treatment, together with three way sign with displays adequate comparison of variable The 55 accidents are all loss central median drainage, was shown as shown in fig. 2. conditions to be made. When of control accidents suggesting provided where practical in an The different displays are ac- such data has been obtained, the excessive speed on the bends de- attempt to reduce both accident tivated by a moisture detection sign is to be commissioned and spite the provision of advisory frequency and severity. device, which is able to detect further data recorded using the speed warning signs throughout Within the Kiama bends sec- weather conditions and the displays triggered by the logic the section and the selective pro- tion, 17 of the accidents oc- amount of precipitation when shown in Table 2. ➤

Figure 2. Variable sign arrangement Table 2. Display logic Normal (Condition1) Raining (Condition2) Wet Road - No Rain Condition1 Condition2 Condition3 (Condition3) Weather Surface Weather Surface Weather Surface Clear Dry Rain Dry Clear Moist Cloudy Moist Cloudy Wet Wet

159/2002 31 Figure 4a. Speed variation during daytime before sign Figure 4b. Speed variation during daytime after sign

Results Dawn Day Dusk Night Detailed results have been ob- Loops1/2 Loops3/4 Loops1/2 Loops3/4 Loops1/2 Loops3/4 Loops1/2 Loops3/4 tained for all conditions. For Condition1 75 68 75 67 75 67 75 67 “Condition1” (clear and dry), a Condition2 74 65 71* 62 72 62 69** 60 full week’s data has been ob- Condition3 73 64 74 65 71 62 71 63 tained providing over 50,000 data sets. This data has been ob- Table 3. Average speeds by time of day tained on days when no rainfall has occurred. For “Condition2” tained for each of these condi- the speed reduction which occurs or moist but no rain is actually and “Condition3”, only 3573 tions. Figures 4 and 5 are an ex- when rain is falling (Fig. 5a & 5b). falling. Success in this area will and 8289 samples respectively ample showing the speed pro- A visual examination of the provide a further option for have been obtained which is files for all three conditions dur- data also shows that the pave- those sites where significant wet considered insufficient to enable ing the day and night times. ment sometimes remains wet or weather problems exist and oth- a full statistical comparison of a Not unexpectedly the early moist in some cases for several er treatments have not been ful- before-situation. In the case of results show that in more ad- hours after the rain has ceased. ly successful in reducing the wet “Condition2”, a range of sam- verse conditions vehicles slow There is also evidence that dew weather accident problem. G ples is also required for differing down to a greater extent in the is responsible for considerable precipitation rates to allow a approach to the curve (Loops periods of a moist pavement. It References study of the sign’s effectiveness 1/2). This speed reduction varies is noticeable that the sample Brisbane, G.J.B., (1996): Driving In Fog in varying rainfall conditions. by time of day with reductions numbers obtained to date for - Putting Research Into Practice. Pro- ceedings 18th ARRB Conference. This would allow further studies during wet conditions of around “Condition3” are around doub- Part 5. (Australian Road Research to be undertaken at a later date 4* km/hr during the day and 6** le those of “Condition2”. Board. Christchurch, New Zealand.) to determine if additional fea- km/h at night. Brisbane, G.J.B., (1999): ITS - Not Just tures would be effective in heavy Further reductions of around Comments For Cities Proceedings ITSA ’99 rain conditions when aquaplan- 8 - 9 km/h occur as the vehicles The results achieved to date (Intelligent Transport Systems ing is more likely to occur (e.g. enter into the curve. However, clearly raise concerns as to the Australia, Adelaide) use of flashing lights when the the early indications (Fig. 4a & behaviour of motorists in condi- rain exceeds a certain intensity.) 4b) are that during the day when tions of wet pavements when This article was printed with the kind The data has also been sepa- the pavement is wet but rain is rain is not falling. The structure permission of ITS Australia. For fur- rated into four different time of not falling (“Condition3”) the of the site arrangements will pro- ther information please refer to the ITS Australia web site at www.ITS-Aus- day periods (dawn, daytime, speed profile of vehicles is simi- vide important information to tralia.com.au. dusk and night) when differing lar to that for dry conditions. allow further analysis to occur. ambient light conditions might This result is also very appar- The provision of the en- Acknowledgement be expected to result in differing ent at dawn and dusk periods hanced signposting is intended Whilst the views and conclusions in driving behaviour. Table 3 shows (these results are not shown due to further reduce the speed of the paper are those of the authors, the the average speeds that occur at to the low sample numbers for vehicles travelling through the assistance and support of the Roads and Traffic Authority in using work ex- the two speed-detection sites be- adverse conditions). curve with particular emphasis amples is greatly acknowledged. fore and after the sign. At night vehicles appear on maintaining speed reduc- Speed profiles were also ob- much more likely to maintain tions when the pavement is wet

Figure 5a. Speed variations at night before sign Figure 5b. Speed variations at night after sign 32 159/2002 The Scope and Future of

What is nowcasting and how does it relate to Nowcasting other weather and climate forecasting methods and practices? Who uses or needs nowcasts? And how far do they depend on at- Walter Dabberdt, Ph.D. Director, Strategic Research mospheric observations? What is the future Vaisala Boulder for operational nowcasting? To answer these Colorado, USA questions, let us first consider the broad spectrum of atmospheric forecasts, beginning with long-range climate predictions, working backwards to conventional short- and medium-range weather forecasts and ending with the ’nowcast’.

Climate modeling terest to climate modeling span decades and even centuries. Their Forecasting the state of the at- focus is on predictions of future mosphere is done in many ways, climate and how the climate will by many groups and organiza- vary according to solar variabili- tions, and over many time scales. ty, the Earth’s Copernican mo- The very long time scales of in- tions, volcanic activity, and ➤

159/2002 33 Monthly and seasonal prepared twice daily and are is- outlooks sued four-to-six hours after the Between forecasts of climate and weather observations that they weather are monthly and season- use. These forecasts extend out al outlooks. Until recently, their as far as seven or more days into typical focus has been on atmos- the future (the forecast duration pheric temperature and precipi- varies according to the particular tation, and how each will vary weather service issuing the fore- from average conditions for a cast – e.g. eight days in Australia

PHOTO COURTESYPHOTO NEC BY AUSTRALIA AND BOM month or a season. A big change and seven days in the U.S.). occurred in 1997, when at least One-to-two day forecasts are one national modeling center considered to be short-range Figure 1. Weather computing accuracy (in terms of predicting changes in made an accurate forecast forecasts, medium-range fore- atmospheric pressure fields) has increased over the decades as improved months in advance of the onset casts are three days and longer. scientific understanding has created higher-resolution models which demand of the major El Niño event of Special high-resolution forecasts the most powerful computers available (source: Australian Bureau of Meteorology). 1997-98. An El Niño is a warm called mesoscale forecasts are tropical episode that is high- now just beginning to come into lighted by warm surface waters operational use in some sectors replacing the upwelling of cold although they are still primarily water along the west coast of a research and special-purpose South America. Significant forecasting tool. Mesoscale fore- changes in global weather pat- casts typically are valid for a pe- terns accompany strong El Niño riod that extends from about events as they also accompany three hours after the time of the its cold-event counterpart, La weather observations that they Niña. During major El Niño use out to one-to-two days later. events, heavy precipitation and They also cover a smaller area flooding can occur along the (model domain) than synoptic west coast of tropical South forecasts. But their greatest at- America, and at subtropical lati- tribute is their ability to provide tudes of North America (Gulf of very high spatial and temporal Mexico) and South America resolution – down to a few kilo- Figure 2. Qualitative depiction of the accuracy of time and place-specific forecasts of convective storms (source: Jim Wilson, NCAR as adapted from (southern Brazil to central Ar- meters or less, and only tens of Browning (1980), Doswell (1986) and Austin et al. (1987). gentina). At the same time, ab- minutes. normally dry conditions occur of greatest public and political in- whose objective is to ’hindcast’ – over northern Australia, Indone- Nowcasting terest, controllable changes in an- predict in reverse – the historical sia and the Philippines in winter The important gap between cur- thropogenic emissions of green- changes in climate that have and summer. Drier than normal rent weather and the onset of va- house gases and aerosols. Cli- been detected with ice cores and conditions are also observed lidity for a mesoscale forecast is mate models are general circula- tree rings. Yet another special as- over southeastern Africa and the domain of the nowcast. In tions models or GCMs that are pect of climate modeling is called northern Brazil, during the approximate terms, the total pe- not unlike those used in day-to- downscaling. It is the process of northern winter season. During riod of interest to nowcasters day weather forecasting [see forecasting regional climate fea- the northern summer season, In- ranges from a few tens of min- box]. However, they must deal tures with greater spatial resolu- dian monsoon rainfall tends to utes up to three-to-six hours. But with the additional challenges tion than is available from the be less than normal. If El Niño in practical terms, current now- that arise from their need to cov- coarse low-resolution global cli- and La Niña forecasts can be casting products for severe er the full globe and very long pe- mate forecasts. The highest reso- made in the future with regulari- weather rapidly lose their validi- riods of time. They must also in- lution of the best global climate ty and adequate skill, the bene- ty after one hour (figure 2). The clude the interactions and feed- models is about 100-200 km, fits to the global community will principle objective of nowcast- backs between the atmosphere, while today’s downscaling activi- be immense -- countries suscep- ing is to provide highly precise oceans, sea ice, land masses, and ties attempt to resolve regional tible to drought and flooding predictions of the intensity, lo- river flows. And they must do climate features on scales of could do much to mitigate these cation, onset and cessation of this in a way that will allow slow- about 40 km. Downscaling seeks prolonged and devastating natu- significant weather-related ly varying, small-scale climate sig- to quantify climate change on ral hazards. events. Rather than making a se- natures of temperature and pre- these higher spatial scales in or- vere-weather forecast of, say, cipitation to be separated from der to better reveal the impacts of “Everyday” weather “scattered afternoon severe the very large signatures and vari- climate change on agriculture, forecasts thunderstorms in the greater St. abilities of short-term weather. water supplies, fish habitats, sus- Traditional synoptic weather Louis area,” a nowcast seeks to Paleoclimate modeling is a tainability and so forth. forecasts are the forecasts that predict the occurrence of a “se- special type of climate modeling are most familiar to us. They are vere thunderstorm with winds in

34 159/2002 excess of 30 meters per second surface mesonets, lightning de- accompanied by golf-ball-size tectors, wind profilers, radioson- hail and intense lightning in the des and satellites, among others. immediate vicinity of the St. Louis Arch between 3:30 pm Nowcasting and 4:15 pm today….” thunderstorms We may not always be aware Forecasting the development of it, but every one of us regular- and movement of severe thun- ly makes our own personal now- derstorms is a major focus of the casts. We instinctively observe nowcasting research community. the types, amounts and changes These storms are both dangerous in the clouds, the direction and and difficult to predict with speed of the wind, the humidity great specificity in regard to lo- and temperature of the air. And cation, timing and severity. Indi- then we make our very own vidual single-cell storms are nowcast – we project what the short-lived, lasting usually less weather will be and how it will than 30 minutes. On the other affect us over the next tens of hand, about half of multi-cell minutes or over the course of storms typically last more than the morning or afternoon. Sci- one hour with their cells split- ence-based nowcasting has the ting and merging throughout and can be grouped into three and visual observations of cloud same objectives, but seeks to use the lifecycle of the storm com- broad categories: 1) extrapola- development. It has been known state-of-the-art-observing tech- plex. And the very large storm tion; 2) convection initiation for some time that human fore- nologies together with expert complexes can last many hours and dissipation; and 3) explicit casters were frequently able to systems, theoretical models and and their movement can be ex- numerical prediction. Extrapola- use these methods with greater frequently also human interven- trapolated with skill. The chal- tion methods are actually of two skill than extrapolation. Recent- tion to make precise very-short- lenge is to develop a suite of types; the steady-state approach ly, new methods are emerging term forecasts. nowcasting methods that can be assumes no change in cell move- that automate the convergence- Numerical forecasts of applied to the full spectrum of ment, size and intensity, while a detection and storm prediction mesoscale and synoptic weather diverse storms. Different now- second type allows for change in process. They are likely to fur- depend on numerical solution casting methods have been cre- intensity and size. The second ther increase predictive skill as of a coupled set of equations for ated over the past 40 years with nowcasting category involves scientific understanding of energy, momentum and mass the goal of effectively predicting the use of expert systems that storm initiation becomes more conservation – see weather pre- the initiation, evolution and dis- seek to predict the initiation and complete, as detailed observa- diction box. They use observa- sipation of convective storm sys- dissipation of convection by tions become more available, tions to specify the initial atmos- tems. These methods have yield- monitoring convergence bound- and as computational advances pheric state and to aid in defined varying degrees of success aries using radar, dense mesonets continue. The third catego- ➤ ing conditions at the boundary of the model domain. Observa- tions are also assimilated into the numerical modeling process as a way to “tune” or adjust the model to the most recent changes in the state of the atmosphere. In contrast, nowcast- Figure 3. Thunderstorm nowcasting map provided by a SAFIR Total ing methods depend heavily on Lightning Detection System dense local observations of showing a multicellular frontal weather, winds, and state vari- storm system over the north of ables, coupled with a variety of France (data courtesy of Meteo empirical and rule-based formu- France). The thunderstorm cells are lations, and on a few theoretical characterized by their total lightning equations and some numerical density (total lightning discharges/min/km2). For each cell modeling as well. Nowcasting the system displays the overall methods vary widely and are tai- contour of the electrically active area lored to fit the application that (blue), and the core with a color they are addressing. But the core coding (green, orange, red) reflecting of the nowcast is a set of highly the cell’s intensity on the basis of the resolved local measurements lightning density. Extrapolated positions and intensities are and observations. These typical- displayed for the next 30 minutes in ly are provided by weather radar, increments of 10 minutes.

159/2002 35 ry of nowcasting convective is Vaisala’s fully physical heat- storm nowcasts. Total lightning storms involves explicit numeri- balance model that predicts site- Bias -0.19ºC activity (IC + CG), with its cal simulation and prediction of specific road surface state and Standard deviation 0.92ºC dominant IC lightning compo- thunderstorms. Some approach- temperature. This allows users to Accuracy1 91.30% nent, is an early indicator of es are being developed that uti- closely monitor potential weath- Reliability2 1.00 storm development. It also cor- lize radar observations of con- er hazards and mobilize re- Miss rate3 10.20% relates closely with storm severi- vergence lines to initialize the sources in sufficient time to take False alarm rate4 7.90% ty. This enables efficient early model, while others do not rely preventive treatment. The mod- detection of storm cells, accurate on these special observations. In el may be run in either Because the IceBreak model tracking information and ad- both cases, explicit numerical mesoscale forecasting mode contains accurate physical repre- vance warning of imminent modeling currently is an emerg- (from 24 to 72 hours ahead) or 3- sentations of all major heat flux- thunderstorm hazards. IC detec- ing nowcasting research tool that hour nowcasting mode. In es, its performance does not de- tion typically provides about ten offers future promise. mesoscale mode, IceBreak uses generate as quickly as rule-based minutes advance warning before After about one hour the as its input data the standard nowcasting roadway applica- the onset of CG lightning activi- skill level of the various nowcast- short-range forecasts of atmos- tions. Indeed the model results ty as well as an order of magni- ing methods decreases rapidly pheric variables, typically from demonstrate significant skill out tude more information for mon- for all convective storms. Skill the nearest mesoscale model to the end of the typical 3-hour itoring and tracking of thunder- levels are higher over longer pe- grid point. IceBreak is currently nowcast period with a gradual storm cells. riods for organized bands of used in mesoscale mode by increase of bias and standard de- Early detection, monitoring convective storm cells and large more than 10 national meteorol- viation as far ahead as 6 hours. and mapping of storm total elec- mesoscale storm systems, but al- ogical services, making it the trical activity, either alone or to- so for nowcasting of non-con- most extensively used ice predic- Vaisala’s SAFIR gether with weather radar and vective events such as freeze tion method worldwide. Lightning System other measurements, is a valu- warnings. Let’s explore a few ex- In nowcast mode, the input Another Vaisala nowcasting ca- able nowcasting tool for many amples of other nowcasting data are real-time local observa- pability focuses on early light- applications. Users include met- methods and their applications. tions from Vaisala’s ROSA road ning and thunderstorm detec- eorological services (SAFIR is weather stations. One extensive tion and forecasting. The Vaisala used by 12 national weather Vaisala’s IceBreak study of operational 3-hour SAFIR Lightning System con- services around the world), as Nowcasting for nowcast performance revealed sists of a network of detection well as electric power and trans- roadways very encouraging results. Using stations that is uniquely capable mission companies, sensitive Vaisala is playing a significant temperature data from 74 sta- of locating at long range all manufacturing industries, fire role in nowcasting applications. tions over a five-month period lightning types – both Intra- and safety personnel, flood man- One such application is ice pre- from October 2000 through Cloud (IC) and Cloud-to- agement districts, and aviation. diction for roadways, which en- February 2001, the evaluation Ground (CG). A central process- Early lightning detection ables road masters to use proac- considered more than 37,000 in- ing system computes the loca- and warning is also critical to the tive anti-icing operations rather dividual nowcasts comprising al- tion of lightning discharges by recreation and outdoor enter- than less effective reactive road most 370,000 data pairs with the triangulation, and also performs tainment sectors where large maintenance practices. IceBreak following results: lightning activity analyses and numbers of individuals can be exposed. In the U.S. alone, lightning caused an annual average of 163 deaths and three times as he NCAR AutoNowcaster is an ongoing development at the National many injuries over the period Center for Atmospheric Research in the U.S. It is a nowcast environ- T 1940-1991. Lightning deaths in ment for collecting weather data and executing algorithms to produce the U.S. exceed by 50% those and display very short-term thunderstorm forecasts. At present, data in- from either tornadoes or floods, corporated into the nowcast environment include Doppler radar data, and are 400% greater than hurri- GOES satellite images, soundings, and surface mesonet data. The soft- cane deaths. ware applications include algorithms for identifying and tracking thunderstorm movement, identifying atmospheric boundaries, retrieving Flood forecasting winds from radar, and a fuzzy-logic engine that allows the user to pro- Two other examples of opera- duce a single, unified nowcast. tional nowcasting systems are The forecast image on the left shows a then-current radar reflectivity flash flood prediction and emer- field together with a 60-minute nowcast for the initiation of a line of se- gency response. Flash flood vere thunderstorms over Washington DC on 2 June 2000. The white poly- analysis and prediction models gons indicate the predicted boundary of echoes with reflectivities >35 are now coming into widespread dBZ. The image on the right shows the actual radar reflectivity field at use in some countries. Flash verification time together with the forecast contour. flood models represent the to- Source: Roberts, R.D., D. Burgess and M. Meister, 2001: Next steps in automated thunderstorm pography, surface conditions, nowcasting: improving performance and forecasting storm severity. Preprints, 30th Conf. on soil moisture and stream net- Radar Meteor., Munich, Germany, Amer. Meteor. Soc., 234-236 works of flood plains and basins,

36 159/2002 and they rely on observations or and Chernobyl in 1986, as well model predictions of precipita- as numerous chemical releases in tion rates and duration to make the U.S. and throughout the Weather prediction short-term forecasts of flooding. world. The important challenge efore weather models can predict the future state of Nowcasting methods use radar for the future is to provide simi- B the atmosphere they must know its present state very to track and extrapolate storm lar capabilities at multiple loca- accurately. This is the primary purpose of a disparate array cell trajectories and estimate the tions, and to make available the of weather measurement instruments and platforms that amount and type of precipita- critical atmospheric measure- include surface weather stations, upper-air radiosonde ob- tion. Radar observations are not ments required to characterize servations, aircraft and ship observations, satellites and var- used in isolation but are fre- atmospheric transport and dis- ious other special-purpose devices. Twice daily at 00 and quently combined with surface persion. This will be especially 12UTC, weather observations are fed into a global telecom- and upper-air lightning detectors important because existing at- munications network, and are then ingested by the nation- data from atmospheric sound- mospheric measurement net- al meteorological services around the world where they are ings, surface weather stations, works have been designed to checked for accuracy, and then projected onto a three-di- rain gauges, cloud radars, wind support the prediction of severe mensional modeling grid. Computer-based forecast models profilers, satellites and virtually weather. On the other hand, the then predict the weather using these observations to first any measurement system avail- most adverse dispersion condi- initialize and then solve a set of mathematical equations able in the area. The challenge is tions are associated with benign that describe the laws governing atmospheric behavior. the availability of adequate and weather regimes. These laws include three equations of atmospheric motion, representative observations. We the thermodynamic equation (representing conservation of will return later to this important The future energy), the so-called gas law or equation of state, and the point. The development of advanced continuity equation (which express the conservation of nowcasting systems for severe mass). Today’s sophisticated forecast models and vastly Emergency response for weather events is ongoing in sev- more capable computers have significantly improved the chemical releases eral countries. Researchers are timeliness and accuracy of weather forecasts and warnings. Emergency response to the acci- exploring several approaches to However the accuracy of weather predictions is still inher- dental or deliberate atmospheric the problem of very short-range ently limited in four areas: releases of toxic chemicals or bi- forecasts that are highly specific 1. the quality, density and representativeness of ological agents is an emerging in time and space. These ap- atmospheric measurements; nowcasting focus. Observations proaches vary widely, ranging 2. the finite power of today’s computers; and mesoscale model predic- from extrapolation to expert sys- 3. our imperfect understanding of and ability to tions are used in conjunction tems to explicit numerical mod- model atmospheric processes, and with atmospheric dispersion eling of storm cells. They all 4. the inherent unpredictability of atmospheric models to predict ground-level share three common needs: da- processes on different scales due to their chaotic exposures downwind of the re- ta, data and even more data! The nature. lease point. Public safety person- observational data must be suffi- Progress in the accuracy and extent of atmospheric nel rely on these predictions to cient to characterize the storm prediction will continue though. A recent report by the quickly develop mitigation and and its environment in great de- U.S. National Academy of Sciences stresses that improved protection strategies. For exam- tail. Herein lies the dilemma: atmospheric measurements are imperative for improved ple, they must decide with very how to ensure that the measure- weather forecasting in the 21st century. G short notice what areas to cor- ment systems will be available don off, and whether it is better where and when they will be to evacuate people in the affect- needed. Part of the answer lies in References Footnotes ed areas or to “shelter in place” determining in advance what lo- Wilson, J.W., N. A. Crook, C. K. Mueller, 1) Accuracy is the percentage of the in by having them remain in- cations will be served by a now- J. Sun and M. Dixon, 1998: Now- time that a given atmospheric state doors. Nowcasting emergency casting capability. But an equally casting Thunderstorms: A Status Re- (e.g. occurrence of frost vs. no frost) is responce systems are being de- important question is “Who will port. Bull. Amer. Meteor. Soc., 79, correctly predicted. signed but very few operational be responsible for supporting 2079-2099. Austin G. L., A. Bellon, P. Dionne and systems exist at present. One no- these nowcasting systems?” Will 2) Reliability is the ratio of the number M. Roch, 1987: On the interaction of times that an atmospheric state is table exception is the National they be a public or a private en- between radar and satellite image predicted relative to the number of ac- Atmospheric Release Advisory terprise? Or will there be public- nowcasting systems and mesoscale nu- tual occurrences. Center (NARAC) at the private partnerships that emerge merical models. Proceedings, Lawrence Livermore National to meet these needs? One thing Mesoscale Analysis & Forecasting, 3) Miss rate is the proportion of Laboratory in California. It has seems certain: nowcasting will European Space Agency SP-282, atmospheric events or states that were Vancover, Canada, 225-228. not predicted. been in existence since 1979 and be an ever more important and Browning, K. A., 1980: Local weather has assisted in supporting emer- valuable component of the forecasting, Proc. R. Soc. London Ser., G 4) False alarm rate is defined as the gency response to more than 70 weather forecasting paradigm. A371, 179-211. proportion of atmospheric events or incidents, including radiation re- Doswell, C.A., 1986: Short-range forecast- states that were predicted but did not leases from the Three Mile Is- ing. Mesoscale Meteorology and Fore- occur. land nuclear power plant in 1979 casting, P. Ray, Ed., Amer. Meteor. Soc., Boston, 793 pp.

159/2002 37 Two German Scientists Win the 16th Professor Vilho Vaisala Award

The winners of the 16th Professor Vilho Vaisala The altitude-dependent devia- popular city for con- Award are two German scientists from tions have in practice meant that ventions, Orlando was RASS technology has not met A the location of the 82 Deutscher Wetterdienst (DWD). Doctor Ulrich the requirements set for opera- nd AMS Annual Meeting from Görsdorf and Mr. Volker Lehmann received tional observation networks. the 13—17 January 2002. The the award for their paper entitled “Enhanced Through their experiments and meeting incorporated 14 sym- comparisons Görsdorf and posia and conferences covering Accuracy of RASS-Measured Temperatures Lehmann were able to identify various topics from environ- Due to an Improved Range Correction”. an insufficient height assign- mental applications, meteorolo- ment in RASS measurements as gy, hydrology and oceanogra- the main cause of measurement phy, to topics on education, he award was presented short-term forecasts the spatial error. They suggested a correc- global change and advanced in November 2001 by and temporal resolution of nu- tion method to compensate for weather interactive processing T the WMO General Sec- merical models should be con- the error, including a variable systems, to name but a few. retary G. O. P. Obasi at the Ger- stantly developed. This requires range correction, vertical veloci- Vaisala attended or participated man Research Centre for Earth data which has a high temporal ty correction and improved tem- in many of the symposia/confer- Sciences in Potsdam. Doctor Ul- and spatial resolution and is ac- perature retrieval. This allowed ences, three of which were: rich Görsdorf and Mr. Volker cessible with remote sensing the systematic deviation from –“Observations, Data Lehmann of the German Mete- methods, such as the Radio the radiosonde measurement re- Assimilation, and orological Service, Lindenberg Acoustic Sounding System for sults to be clearly reduced. Görs- Probabilistic Prediction” Observatory were recognized for temperature measurements. dorf and Lehmann’s research in- –“Interactive Information their scientific work on the meas- troduces an important step to- and Processing Systems” urement of atmospheric temper- Identifying wards the increased use of –“Integrated Observing ature with the Radio Acoustic the measurement error RASS measurements in the Systems”. Sounding System (RASS). The and developing worldwide operational aerologi- winning research paper “En- a correction method cal network. RASS instruments Short courses and special hanced Accuracy of RASS-Mea- In their winning paper Dr. Görs- are normally used as a comple- conferences and sessions were al- sured Temperatures Due to an dorf and Mr. Lehmann de- mentary instrument with wind so scheduled for participation. Improved Range Correction” scribed the extensive compara- profilers so that both vertical For the first time the meet- was published in the Journal of tive study they carried out at the wind and temperature profiles ing also featured a special event Atmospheric and Oceanic Tech- Meteorological Observatory Lin- can be presented within the for the local community, the nology, vol. 17, no 4, 2000. denberg. The study investigated same display software. AMS WeatherFest: a communi- the systematic errors in tempera- cations workshop and student High resolution data for ture measurement that occur Designed to encourage conference. Additionally, a Pres- the enhanced accuracy with RASS at lower altitudes in research programs idential Policy Forum was held, of forecasts comparison with radiosonde The Professor Vilho Vaisala devoted to societal aspects of To improve the accuracy of and tethersonde measurements. Award was established in 1985 meteorology, especially the role and is administrated by the of AMS in meeting society’s World Meteorological Organiza- needs. In the forum experts tion (WMO). It is awarded to shared their views on society’s encourage and stimulate interest weather and climate information in important research supportive needs. More than 130 compa- of WMO’s programs, in the nies took part in the exhibition field of meteorological and cli- that was arranged in conjunction matic observation methods and with the meeting. instruments. G Vaisala attendees at the AMS Meeting each had their role to play whether it was meeting with The award was presented in November 2001 by the WMO General business partners and customers, Secretary G. O. P. Obasi at the German Research Centre for Earth Sciences presenting oral papers, attending in Potsdam. presentations and courses,

38 159/2002 Vaisala showcased a number of products and technologies at AMS in Orlando, Florida.

Vaisala Success at the Vaisala Centralizes 82nd American USA Manufacturing Meteorological Society Operations in Boulder Annual Meeting, The Vaisala Group will centralize its US man- January 2002 ufacturing operations into one location, Boulder, Colorado, from the present five pro- The AMS 82nd Annual Meeting was held 13–17 duction sites in the USA. This reflects Vaisala‘s January 2002 in Orlando, Florida. The event at- commitment to the North American market tracted more than 3000 attendees, including and to its customers. Vaisala offices in registrants, students, exhibitors and guests. The Boston, Columbus and Sunnyvale will contin- theme of the meeting was “Generating Envi- ue to function as sales, customer service and ronmental Information and Services” and product development locations. Vaisala participated to the full at the accompa- nying exhibition where more than 130 compa- uring the last few years started in March 2002 and the nies were showcasing their products. the North American first phase, which will be com- D share of Vaisala Group’s pleted by the end of the year, sales has been increasing and will include 40,000 sq. feet of of- this increase is expected to con- fice and manufacturing space. tinue. “The US market has be- The investment is valued at come increasingly important for USD 4.7 million. us, and its share of the Group’s The dropsonde production net sales has been increasing. By from Boston, the aviation weath- “manning the booth”, or pro- –Vaisala Rocketsonde and centralizing our operations we er system production and after moting new products and other upper air products want to show our commitment sales services from Columbus, Vaisala - as well as everyone con- –new 16-channel GOES to the North American market and the weather station and sys- tinually establishing contacts. Direct Readout Ground and to our customers,” says tems production from Sunny- The activity level was high and station Pekka Ketonen, President and vale will be relocated to Boulder the image portrayed by Vaisala –scale models of the SAFIR CEO of Vaisala Group. By cen- by the end of 2002. The wind expansive. Vaisala introduced and LAP®-3000 Wind- tralizing operations Vaisala aims sensor production will be relo- AMS attendees to a business profiler. at enhancing productivity and cated from Sunnyvale to the unit that was new from last year Philippe Richard presented a efficiency. Several important Vaisala office in Helsinki, Fin- – the Wind Profiler group - and a paper on SAFIR Total Lightning meteorological research insti- land. At the same time, out- new division, the Remote Sens- Detection Technology. Other tutes and laboratories that sourcing will be increased. For ing Division. In its spacious papers presented by Vaisala in- Vaisala works in close coopera- Vaisala customers in the U.S. the booth, Vaisala showcased a cluded two by Pekka Utela: one tion with are also located in relocation does not implicate number of products: on the new Vaisala FS11 Visibili- Boulder. any major changes, since Vaisala –new optical sensors - Vaisala ty Sensor which has a unique offices in Boston, Columbus and FS11 Visibility Sensor and window contamination com- New facilities to be Sunnyvale will continue as sales, Vaisala LD40 Ceilometer pensation method, and the sec- built in Boulder customer service and product de- – a full IceCast Road Weather ond on a multiple instrument Vaisala will build a new produc- velopment locations after the Station and TACMET sky condition algorithm for tion plant in the Colorado Tech production unit relocation. G station were erected ceilometers. G Center area. Construction was

159/2002 39 Europe North America

Vaisala Oyj Vaisala Inc. P.O. Box 26, FIN-00421 Helsinki 100 Commerce Way FINLAND Woburn, MA 01801-1068 Telephone: +358 9 894 91 USA Telefax: +358 9 8949 2227 Telephone: +1 781 933 4500 Telefax: +1 781 933 8029 Vaisala Malmö Drottninggatan 1 D Vaisala Inc. S - 212 11 Malmö Columbus Operations SWEDEN 7450 Industrial Parkway Telephone: +46 40 298 991, Plain City, Ohio 43064-9005 in Sweden: 0200 848 848 USA Telefax.: +46 40 298 992, Telephone: +1 614 873 6880 in Sweden: 0200 849 849 Telefax: +1 614 873 6890

Vaisala GmbH Vaisala Inc. Achter de Weiden 10 Boulder Operations D-22869 Schenefeld 8401 Base Line Road As of July 1, 2002, new address: Boulder, CO 80303-4715 Schnackenburgallee 41 USA D-22525 Hamburg Telephone: +1 303 499 1701 GERMANY Telefax: +1 303 499 1767 Telephone: +49 40 839 03 207 Telefax: +49 40 839 03 211 Vaisala Inc. 5600 Airport Boulevard Vaisala Impulsphysik GmbH Boulder, CO 80301-2340 Achter de Weiden 10 USA D-22869 Schenefeld Telephone: +1 303 443 2378 GERMANY Fax: +1 303 443 1628 As of July 1, 2002, new address: Schnackenburgallee 41, D-22525 Hamburg Vaisala Inc. GERMANY Sunnyvale Operations Telephone: +49 40 839 030 1288 Reamwood Ave. Telefax: +49 40 839 03 110 Sunnyvale, CA 94089-2233 USA Vaisala GmbH Telephone: +1 408 734 9640 Bonn Office Telefax: +1 408 734 0655 Adenauerallee 46 a D-53110 Bonn Vaisala-GAI Inc. GERMANY 2705 East Medina Road Telephone: +49 228 912 5110 Tucson, Arizona 85706, USA Telefax: +49 228 912 5111 Telephone: +1 520 806 7300 Telefax: +1 520 741 2848 Vaisala GmbH U.S. Toll Free 1 800 283 4557 Bremerhaven Office Buchtstrasse 45 Vaisala Inc. Regional Office 27570 Bremerhaven Canada GERMANY P.O. Box 2241, Station “B” Telephone: +49 471 170 1655 London Telefax: +49 471 170 1755 Ontario N6A 4E3 CANADA Vaisala GmbH Telephone: +1 519 679-9563 Hamburg Office Telefax: +1 519 679-9992 Axel-Springer-Platz 2 D - 20355 Hamburg Asia and Pacific GERMANY Vaisala KK Telephone: +49 40 3410 7879 42 Kagurazaka 6-Chome Telefax: +49 40 3410 7887 Shinjuku-Ku As of July 1, 2002, new contact information: Tokyo 162-0825 Schnackenburgallee 41 JAPAN D-22525 Hamburg, GERMANY Telephone: +81 3 3266 9611 Telephone: +49 40 839 03 111 Telefax: +81 3 3266 9610 Telefax: +49 40 839 03 122 Vaisala KK Vaisala GmbH Osaka Branch Stuttgart Office 1-12-15, Higashimikuni Pestalozzi Str. 8 Yodogawa-Ku, Osaka 532-0002 D-70563 Stuttgart JAPAN GERMANY Telephone: +81 6 6391 2441 Telephone: +49 711 734 057 Telefax: +81 6 6391 2442 Telefax: +49 711 735 6340 Vaisala Pty Ltd Vaisala Ltd 3 Guest Street Birmingham Operations Hawthorn, VIC 3122 Vaisala House AUSTRALIA 349 Bristol Road Telephone: +61 3 9818 4200 Birmingham B5 7SW Telefax: +61 3 9818 4522 UNITED KINGDOM ABN 58 006 500 616 Telephone: +44 121 683 1200 Telefax: +44 121 683 1299 Vaisala Beijing Representative Office Vaisala Ltd Wangfujing Grand Hotel Newmarket Office Room 518 - 520 Suffolk House 57, Wangfujing Street Fordham Road Beijing 100006 Newmarket PEOPLE’S REPUBLIC OF Suffolk CB8 7AA CHINA UNITED KINGDOM Telephone: +86 10 6522 4041 Telephone: +44 1638 674 400 +86 10 6522 4050 Telefax: +44 1638 674 411 +86 10 6522 4151 Telefax: +86 10 6522 4051 Vaisala SA 2, rue Stéphenson (escalier 2bis) Vaisala Regional Office Malaysia F-78181 Saint-Quentin-en-Yvelines Level 36, Menara Citibank Cedex 165 Jalan Ampang FRANCE 50450 Kuala Lumpur Telephone: +33 1 3057 2728 MALAYSIA Telefax: +33 1 3096 0858 Telephone: +60 3 2169 7776 Telefax: +60 3 2169 7775 Vaisala SA 7, Europarc Ste-Victoire F-13590 Meyreuil FRANCE Telephone: +33 4 4212 6464 C210019en 2002-05 Telefax: +33 4 4212 6474