DOCSLIB.ORG

Accuracy Matters in Radiosonde Measurements

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Accuracy Matters in Radiosonde Measurements Accuracy Matters in Radiosonde Measurements / WHITE PAPER WEA-MET-G-Accuracy-Matters-in-Radiosonde-Measurements-White-Paper-B211548EN-A.indd 1 11.3.2016 10.37 Table of Contents Introduction ................................................................................................................................................. 3 Quality of Radiosonde Measurements is Critical ............................................................................................ 5 Convective Weather and Thunderstorms ...................................................................................................... 6 Radiosondes in Forecasting Convection ..................................................................................................... 6 Case Study 1: Convective Weather ............................................................................................................. 8 Case Study 2: Weak Convection ................................................................................................................10 Winter Weather ...........................................................................................................................................12 Radiosondes in Forecasting Winter Precipitation ......................................................................................13 Case Study 3: Freezing Rain and Ice Storm ................................................................................................15 Numerical Weather Prediction ..................................................................................................................... 17 Radiosondes in Validating NWP Models ....................................................................................................18 Case Study 4: Fog .....................................................................................................................................18 Meteorological Indices ...............................................................................................................................20 Impact of Radiosonde Data Quality ...........................................................................................................21 Radiosonde Pressure Measurement ............................................................................................................ 23 GPS-based Pressure ................................................................................................................................ 24 Sensor-based Pressure ............................................................................................................................ 25 Case Study 5: Tropical Cyclone ................................................................................................................ 26 Radiosonde Data in Climatology ................................................................................................................. 27 Radiosonde Accuracy Matters .................................................................................................................... 28 Further reading ...................................................................................................................................... 29 2 WEA-MET-G-Accuracy-Matters-in-Radiosonde-Measurements-White-Paper-B211548EN-A.indd 2 11.3.2016 10.37 Introduction Radiosondes measure critical atmospheric variables with accuracy and precision that cannot be obtained with other meteorological observations. Radiosondes are unique instruments as they provide continuous, detailed profiles from the ground to altitudes of 30 km and above. The quality and reliability of the measurements are essential. Even small inaccuracies in the profiles can prevent the forecaster from observing critical details and making correct conclusions. The chapters in this document provide information on the importance of radiosonde measurement accuracy, and how accuracy helps to successfully forecast high impact weather. Graphs, tables, and case study summaries illustrate how correct or incorrect observations of temperature inversion layers, ice forming layers, humidity, and other atmospheric properties can change a forecast in various weather situations. a) Deep convection d) Freezing rain Sounding Modified sounding: profile wet-bulb error Ice formation Shallow layer T < -10 °C ➔ Probable ice formation Elevated warm Tmax = 1.9 °C ➔ Partial melting of layer ice ➔ Solid and liquid can occur Surface Tsurface < 0 °C ➔ Rain will freeze on the ground ➔ Ice accumulation / sleet Forecast Ice pellets (more probable) or freezing rain or mix 3 WEA-MET-G-Accuracy-Matters-in-Radiosonde-Measurements-White-Paper-B211548EN-A.indd 3 11.3.2016 10.37 4 WEA-MET-G-Accuracy-Matters-in-Radiosonde-Measurements-White-Paper-B211548EN-A.indd 4 11.3.2016 10.37 Quality of Radiosonde Measurements is Critical The radiosonde is unique among important that radiosonde sensors or even entirely mask the feature other observation systems in work reliably in changing conditions in the profile. In summertime that it provides a complete throughout the harsh environment this may lead the meteorologist vertical profiling of the initial of the upper atmosphere. Erroneous to conclude that, for example, state of the atmospheric analysis measurements could entirely convection will start earlier in that drives numerical weather change the forecast conclusions. For the day with less energy released prediction models. Furthermore, example, the following challenging into convection, or to predict that meteorologists are interested conditions could occur in cloudy rain will start earlier and cool the in several phenomena that are weather situations: land surface, with thunderstorms visible in the radiosonde data, unlikely to form. including cloud layers, dry layers, • As the radiosonde emerges from temperature inversions, jet streams a cloud, the temperature sensor • If the humidity sensor freezes and wind shear. Radiosondes also is in danger of experiencing a while passing through clouds, have an important role in providing ‘wet bulb’ error, generated as the radiosonde may incorrectly long-term high-quality time series water or ice evaporates from the continue measuring high relative of climatology trends of various surface of the sensor. This may humidity. The sensitivity to detect parameters. lead to incorrectly measuring cloud layers is reduced. For the strength of the temperature example, erroneously predicted These applications place a high inversion. Such erroneous upper cloud layers would block demand on the accuracy and observations can reduce the the solar radiation from reaching precision of the measurement. It is magnitude of the detected layer the ground and thus inhibit convection. 5 WEA-MET-G-Accuracy-Matters-in-Radiosonde-Measurements-White-Paper-B211548EN-A.indd 5 11.3.2016 10.37 Convective Weather and Thunderstorms Figure 1. Model radiosonde profiles of temperature, dew-point and wind, showing characteristic features that predict various types of convection. See further explanations in Table 1. During convection, warm air near Radiosondes in Forecasting Convection the ground starts rising until it cools and becomes balanced with In a convective situation, the Radiosonde measurements its surroundings. The following analysis of the latest radiosonde summarize the state of the factors are needed for atmospheric profiles in the region is an essential atmosphere and give the basis for convection to occur: enough step in forecasting. Convection understanding how the weather will moisture at the height from which is still poorly represented in the evolve in the next hours. Figure 1 convection initiates, instability, numerical weather prediction shows examples of three basic types and a lifting mechanism. Strong models due to inadequate spatial of convective weather and how they convection in humid atmosphere and temporal resolutions and the can be forecasted from radiosonde can lead to thunderstorms. difficulty to quantify humidity. profiles. a) Deep convection The air near the surface is warm, moist and well-mixed. There is a strong temperature inversion and enough convective inhibition (CIN) to prevent convection from beginning too early and thus enables convective available potential energy (CAPE) to build up. A relatively rapid decrease in temperature with height in the middle troposphere results in small stability. Cloud layers affect the amount of solar warming on the surface. If air near the surface 6 WEA-MET-G-Accuracy-Matters-in-Radiosonde-Measurements-White-Paper-B211548EN-A.indd 6 11.3.2016 10.37 Factor Explanation Interpretation in radiosonde profile Temperature inversion Layer of warmer air above cool A temperature inversion prevents air. ascending air from penetrating it and helps build up convective energy. A strong inversion may prevent convection entirely. Dew-point temperature The temperature where Humid and dry layers in the profile condensation begins. Moisture indicate the amount of energy available content of air is high when in the atmosphere. the dew-point is close to air A deep dry layer can eat moisture from temperature. lower layers and thus prevent deep convection. CAPE and CIN Meteorological indices for Calculated from radiosonde profile. convective available potential Indicate the stability of the atmosphere. energy and convective inhibition. Vertical wind shear Change in wind speed and Vertical wind shear is needed for direction over height. thunderstorms to become severe and long-lasting. Lifted
Load more

Recommended publications
  • Frequency Plan, 2004
    BOTSWANA RADIO FREQUENCY PLAN, 2004 . Botswana Radio Frequency Plan, 2004 Published on 16 April 2004. TABLE OF CONTENTS Part 1 PRELIMINARY 1. Introduction. 2. Definitions. 3. Interpretation of Table of Frequency Allocations. Part II TABLE OF FREQUENCY ALLOCATIONS 4. Table of Frequency Allocations. 5. ITU Radio Regulations Footnotes National Radio Frequency Plan 2004 Page 1 BOTSWANA RADIO FREQUENCY PLAN, 2004 . PART 1 - PRELIMINARY 1. Introduction The basis for the Botswana Radio Frequency Band Plan is Section 43 of the Telecommunications Act, 1996 [No. 15 of 1996] and Article 5 of the International Telecommunication Union (ITU) Radio Regulations. The ITU Radio Regulations are annexed to the ITU Convention and are revised by the ITU World Radiocommunication Conference, normally held every three years. The Botswana frequency allocations are broadly in consonance with the ITU requirements for Region 1, within which Botswana falls under 2. Definitions In these regulations, unless the context otherwise requires, “Act” refers to the Telecommunications Act No. 15 of 1996. “Administration” means a government or public authority of a country that is responsible for giving effect to the obligations of the country as a member of International Telecommunications Union (ITU). Botswana Telecommunication Authority (BTA) is the Botswana administration. “Additional Allocation” means an allocation, in the form of Footnote, which is added in this area or in this country to the services or services which are indicated in Table of Frequency allocation. “Aeronautical Mobile Service” a mobile service between aeronautical stations and aircraft stations, or between aircraft stations, in which survival craft stations may participate; emergency position-indicating radiobeacon stations may also participate in this service on designated distress and emergency frequencies.
    [Show full text]
  • Lecture 7. More on BL Wind Profiles and Turbulent Eddy Structures in This
    Atm S 547 Boundary Layer Meteorology Bretherton Lecture 7. More on BL wind profiles and turbulent eddy structures In this lecture… • Stability and baroclinicity effects on PBL wind and temperature profiles • Large-eddy structures and entrainment in shear-driven and convective BLs. Stability effects on overall boundary layer structure Above the surface layer, the wind profile is also affected by stability. As we mentioned previously, unstable BLs tend to have much more well-mixed wind profiles than stable BLs. Fig. 1 shows observations from the Wangara experiment on how the velocity defects and temperature profile are altered by BL stability (as measured by H/L). Within stability classes, the velocity profiles collapse when scaled with a velocity scale u* and the observed BL depth H, but there is a large difference between the stability classes. Baroclinicity We would expect baroclinicity (vertical shear of geostrophic wind) to also affect the observed wind profile. This is most easily seen for a laminar steady-state Ekman layer in a geostrophic wind with constant vertical shear ug(z) = (G + Mz, Nz), where M = -(g/fT0)∂T/∂y, N = (g/fT0)∂T/∂x. The momentum equations and BCs are: -f(v - Nz) = ν d2u/dz2 f(u - G - Mz) = ν d2v/dz2 u(0) = 0, u(z) ~ G + Mz as z → ∞. v(0) = 0, v(z) ~ Nz as z → ∞. The resultant BL velocity profile is the classical Ekman layer with the thermal wind added onto it. u(z) = G(1 - e-ζ cos ζ) + Mz, (7.1) 1/2 v(z) = G e- ζ sin ζ + Nz.
    [Show full text]
  • Imet-4 Radiosonde 403 Mhz GPS Synoptic
    iMet-4 Radiosonde 403 MHz GPS Synoptic Technical Data Sheet Temperature and Humidity Radiosonde Data Transmission The iMet-4 measures air temperature with a The iMet-4 radiosonde can transmit to an small glass bead thermistor. Its small size effective range of over 250 km*. minimizes effects caused by long and short- wave radiation and ensures fast response times. A 6 kHz peak-to-peak FM transmission maximizes efficiency and makes more channels The humidity sensor is a thin-film capacitive available for operational use. Seven frequency polymer that responds directly to relative selections are pre-programmed - with custom humidity. The sensor incorporates a temperature programming available. sensor to minimize errors caused by solar heating. Calibration Pressure and Height The iMet-4’s temperature and humidity sensors are calibrated using NIST traceable references to As recommended by GRUAN3, the iMet-4 is yield the highest data quality. equipped with a pressure sensor to calculate height at lower levels in the atmosphere. Once Benefits the radiosonde reaches the optimal height, pressure is derived using GPS altitude combined • Superior PTU performance with temperature and humidity data. • Lightweight, compact design • No assembly or recalibration required The pressure sensor facilitates the use of the • GRUAN3 qualified (pending) sonde in field campaigns where a calibrated • Status LED indicates transmit frequency barometer is not available to establish an selection and 3-D GPS solution accurate ground observation for GPS-derived • Simple one-button user interface pressure. For synoptic use, the sensor is bias adjusted at ground level. Winds Data from the radiosonde's GPS receiver is used to calculate wind speed and direction.
    [Show full text]
  • Comparison Between GPS Radio Occultation and Radiosonde Sounding Data
    Comparison Between GPS Radio Occultation and Radiosonde Sounding Data Dione Rossiter Academic Affiliation, Fall 2003: Senior University of California, Berkeley SOARS® Summer 2003 Science Research Mentors: Christian Rocken, Bill Kuo, and Bill Schreiner Writing and Communications Mentor: David Gochis Community Mentor: Annette Lampert Peer Mentor: Pauline Datulayta ABSTRACT Global Positioning System (GPS) Radio Occultation (RO) is a new technique for obtaining profiles of atmospheric properties, specifically: refractivity, temperature, pressure, water vapor pressure in the neutral atmosphere, and electron density in the ionosphere. The data received from GPS RO contribute significant amounts of information to a range of fields including meteorology, climate, ionospheric research, geodesy, and gravity. Low-Earth orbiting satellites, equipped with a GPS receiver, track GPS radio signals as they set or rise behind the Earth. Since GPS signals are refracted (delayed and bent) by the Earth's atmosphere, these data are used to infer information about atmospheric refractivity. Before the GPS RO data are used for research and operations, it is essential to assess their accuracy. Therefore, this research provided quantitative estimates of the accuracy of GPS RO when compared with measurements of known accuracy. Profile statistics (mean, standard deviation, standard error) were computed as a function of altitude to quantify the errors. Comparing RO data with nearby (300km; 2hr) radiosonde data yielded small mean error for all of the statistical plots generated, affirming that the RO technique is accurate for measuring atmospheric properties. Comparison of RO data with sounding data from different radiosonde systems showed that the RO technique was of high enough accuracy to differentiate differences in performance of various types of radiosonde systems.
    [Show full text]
  • GPS-Based Measurement of Height and Pressure with Vaisala Radiosonde RS41
    GPS-Based Measurement of Height and Pressure with Vaisala Radiosonde RS41 WHITE PAPER Table of Contents CHAPTER 1 Introduction ................................................................................................................................................. 4 Executive Summary of Measurement Performance ............................................................................. 5 CHAPTER 2 GPS Technology in the Vaisala Radiosonde RS41 ........................................................................................... 6 Radiosonde GPS Receiver .................................................................................................................. 6 Local GPS Receiver .......................................................................................................................... 6 Calculation Algorithms ..................................................................................................................... 6 CHAPTER 3 GPS-Based Measurement Methods ............................................................................................................... 7 Height Measurement ......................................................................................................................... 7 Pressure Measurement ..................................................................................................................... 7 Measurement Accuracy..................................................................................................................... 8 CHAPTER
    [Show full text]
  • ESSENTIALS of METEOROLOGY (7Th Ed.) GLOSSARY
    ESSENTIALS OF METEOROLOGY (7th ed.) GLOSSARY Chapter 1 Aerosols Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human (anthropogenic) sources, such as the burning of fossil fuels. Sulfur-containing fossil fuels, such as coal, produce sulfate aerosols. Air density The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3 or kg/m3. Also See Density. Air pressure The pressure exerted by the mass of air above a given point, usually expressed in millibars (mb), inches of (atmospheric mercury (Hg) or in hectopascals (hPa). pressure) Atmosphere The envelope of gases that surround a planet and are held to it by the planet's gravitational attraction. The earth's atmosphere is mainly nitrogen and oxygen. Carbon dioxide (CO2) A colorless, odorless gas whose concentration is about 0.039 percent (390 ppm) in a volume of air near sea level. It is a selective absorber of infrared radiation and, consequently, it is important in the earth's atmospheric greenhouse effect. Solid CO2 is called dry ice. Climate The accumulation of daily and seasonal weather events over a long period of time. Front The transition zone between two distinct air masses. Hurricane A tropical cyclone having winds in excess of 64 knots (74 mi/hr). Ionosphere An electrified region of the upper atmosphere where fairly large concentrations of ions and free electrons exist. Lapse rate The rate at which an atmospheric variable (usually temperature) decreases with height. (See Environmental lapse rate.) Mesosphere The atmospheric layer between the stratosphere and the thermosphere.
    [Show full text]
  • The Impact of Dropsonde and Extra Radiosonde Observations During NAWDEX in Autumn 2016
    FEBRUARY 2020 S C H I N D L E R E T A L . 809 The Impact of Dropsonde and Extra Radiosonde Observations during NAWDEX in Autumn 2016 MATTHIAS SCHINDLER Meteorologisches Institut, Ludwig-Maximilians-Universitat,€ Munich, Germany MARTIN WEISSMANN Hans-Ertel Centre for Weather Research, Deutscher Wetterdienst, Munich, Germany, and Institut fur€ Meteorologie und Geophysik, Universitat€ Wien, Vienna, Austria ANDREAS SCHÄFLER Institut fur€ Physik der Atmosphare,€ Deutsches Zentrum fur€ Luft- und Raumfahrt, Oberpfaffenhofen, Germany GABOR RADNOTI European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom (Manuscript received 2 May 2019, in final form 18 November 2019) ABSTRACT Dropsonde observations from three research aircraft in the North Atlantic region, as well as several hundred additionally launched radiosondes over Canada and Europe, were collected during the international North Atlantic Waveguide and Downstream Impact Experiment (NAWDEX) in autumn 2016. In addition, over 1000 dropsondes were deployed during NOAA’s Sensing Hazards with Operational Unmanned Technology (SHOUT) and Reconnaissance missions in the west Atlantic basin, supplementing the conven- tional observing network for several intensive observation periods. This unique dataset was assimilated within the framework of cycled data denial experiments for a 1-month period performed with the global model of the ECMWF. Results show a slightly reduced mean forecast error (1%–3%) over the northern Atlantic and Europe by assimilating these additional observations, with the most prominent error reductions being linked to Tropical Storm Karl, Cyclones Matthew and Nicole, and their subsequent interaction with the midlatitude waveguide. The evaluation of Forecast Sensitivity to Observation Impact (FSOI) indicates that the largest impact is due to dropsondes near tropical storms and cyclones, followed by dropsondes over the northern Atlantic and additional Canadian radiosondes.
    [Show full text]
  • A Strategy for Representing the Effects of Convective Momentum Transport
    PUBLICATIONS Journal of Advances in Modeling Earth Systems RESEARCH ARTICLE A strategy for representing the effects of convective 10.1002/2014MS000417 momentum transport in multiscale models: Evaluation using a Key Points: new superparameterized version of the Weather Research and The proposed formulation is general enough to allow up or down- Forecast model (SP-WRF) gradient CMT The net effect of the formulation is to S. N. Tulich1,2 produce large-scale circulation A novel superparameterized version 1CIRES, University of Colorado, Boulder, Colorado, USA, 2Physical Sciences Division, NOAA Earth System Research of the WRF model is described and Laboratory, Boulder, Colorado, USA evaluated Correspondence to: Abstract This paper describes a general method for the treatment of convective momentum transport S. N. Tulich, (CMT) in large-scale dynamical solvers that use a cyclic, two-dimensional (2-D) cloud-resolving model (CRM) [email protected] as a ‘‘superparameterization’’ of convective-system-scale processes. The approach is similar in concept to traditional parameterizations of CMT, but with the distinction that both the scalar transport and diagnostic Citation: Tulich, S. N. (2015), A strategy for pressure gradient force are calculated using information provided by the 2-D CRM. No assumptions are representing the effects of convective therefore made concerning the role of convection-induced pressure gradient forces in producing up or momentum transport in multiscale down-gradient CMT. The proposed method is evaluated using a new superparameterized version of the models: Evaluation using a new superparameterized version of the Weather Research and Forecast model (SP-WRF) that is described herein for the first time.
    [Show full text]
  • Coastal Weather Program
    Commandant 2100 Second Street, S.W. United States Coast Guard Washington, DC 20593-0001 (202) 267-1450 COMDTINST 3140.3D 13 JAN 1988 COMMANDANT INSTRUCTION 3140.3D Subj: Coastal Weather Program 1. PURPOSE. To set forth policy for weather observation, reporting, and dissemination from Coast Guard shore units and offshore light stations; and, to direct the coordination with the National Weather Service (NWS) for these activities. 2. DIRECTIVES AFFECTED. Commandant Instruction 3140.3C is canceled. 3. PROGRAM OBJECTIVES. To support the National Weather Service in conducting its federally-mandated weather forecasting and dissemination program by: a. Designating those stations and units required to report weather observations. b. Ensuring that weather reports are made in the suitable format as prescribed by the NWS. c. Ensuring that uniform and timely communication procedures and methods are used to convey this information to the NWS. d. Providing procedures for units not participating in a regular weather reporting program which may be required to make weather observations in support of NWS special programs. 4. POLICY. Title 14 Section 147 of the U.S. Code authorizes the Commandant to procure, maintain, and make available facilities and assistance for observing, investigating, and communicating weather phenomena and for disseminating weather data, forecasts and warnings in cooperation with the Director of the National Weather Service. To this end the Commandant supports a program to ensure the high quality and quantity of weather observations for NWS marine weather forecasts. The Coast Guard, as a user, depends upon high quality forecasts for our missions in the marine environment. COMDTINST 3140.3D 13 JAN 1988 5.
    [Show full text]
  • P7.1 a Comparative Verification of Two “Cap” Indices in Forecasting Thunderstorms
    P7.1 A COMPARATIVE VERIFICATION OF TWO “CAP” INDICES IN FORECASTING THUNDERSTORMS David L. Keller Headquarters Air Force Weather Agency, Offutt AFB, Nebraska 1. INTRODUCTION layer parcels are then sufficiently buoyant to rise to the Level of Free Convection (LFC), resulting in convection The forecasting of non-severe and severe and possibly thunderstorms. In many cases dynamic thunderstorms in the continental United States forcing such as low-level convergence, low-level warm (CONUS) for military customers is the responsibility of advection, or positive vorticity advection provide the Air Force Weather Agency (AFWA) CONUS Severe additional force to mechanically lift boundary layer Weather Operations (CONUS OPS), and of the Storm parcels through the inversion. Prediction Center (SPC) for the civilian government. In the morning hours, one of the biggest Severe weather is defined by both of these challenges in severe weather forecasting is to organizations as the occurrence of a tornado, hail determine not only if, but also where the cap will break larger than 19 mm, wind speed of 25.7 m/s, or wind later in the day. Model forecasts help determine future damage. These agencies produce ‘outlooks’ denoting soundings. Based on the model data, severe storm areas where non-severe and severe thunderstorms are indices can be calculated that help measure the expected. Outlooks are issued for the current day, for predicted dynamic forcing, instability, and the future ‘tomorrow’ and the day following. The ‘day 1’ forecast state of the capping inversion. is normally issued 3 to 5 times per day, the ‘day 2’ and One measure of the cap is the Convective ‘day 3’ forecasts less frequently.
    [Show full text]
  • Allianz Risk Barometer
    ALLIANZ GLOBAL CORPORATE & SPECIALTY ALLIANZ RISK BAROMETER IDENTIFYING THE MAJOR BUSINESS RISKS FOR 2021 The most important corporate perils for the next 12 months and beyond, based on the insight of 2,769 risk management experts from 92 countries and territories. About Allianz Global Corporate & Specialty Allianz Global Corporate & Specialty (AGCS) is a leading global corporate insurance carrier and a key business unit of Allianz Group. We provide risk consultancy, Property-Casualty insurance solutions and alternative risk transfer for a wide spectrum of commercial, corporate and specialty risks across 10 dedicated lines of business. Our customers are as diverse as business can be, ranging from Fortune Global 500 companies to small businesses, and private individuals. Among them are not only the world’s largest consumer brands, tech companies and the global aviation and shipping industry, but also wineries, satellite operators or Hollywood film productions. They all look to AGCS for smart answers to their largest and most complex risks in a dynamic, multinational business environment and trust us to deliver an outstanding claims experience. Worldwide, AGCS operates with its own teams in 31 countries and through the Allianz Group network and partners in over 200 countries and territories, employing over 4,450 people. As one of the largest Property-Casualty units of Allianz Group, we are backed by strong and stable financial ratings. In 2019, AGCS generated a total of €9.1 billion gross premium globally. www.agcs.allianz.com/about-us/about-agcs.html METHODOLOGY CONTENTS The 10th Allianz Risk Barometer is the biggest yet, incorporating the views of a record 2,769 respondents from 92 countries and territories.
    [Show full text]
  • Baseline Climatology of Sounding Derived Parameters Associated with Deep Moist Convection ______
    BASELINE CLIMATOLOGY OF SOUNDING DERIVED PARAMETERS ASSOCIATED WITH DEEP MOIST CONVECTION _________________________________________ Jeffrey P. Craven NOAA/National Weather Service Forecast Office Jackson, Mississippi and Harold E. Brooks NOAA/National Severe Storms Laboratory Norman, Oklahoma Abstract access to explicit forecast parameters such as vertical wind shear and lapse rates possible. This has allowed A baseline climatology of several parameters common- forecasters to finally use techniques developed over half ly used to forecast deep, moist convection is developed a century ago in a real-time operational setting (e.g., using an extensive sample of upper-air observations. Showalter and Fulks 1943). Surface to 6 km above Previous climatologies often contain a limited number of ground level (AGL) magnitude of vector difference of cases or do not include null cases, which limit their fore- wind (hereafter 0-6 km shear) and 700-500 hPa lapse cast utility. Three years of evening (0000 UTC) rawin- rates are used frequently in assessing severe potential, sonde data (approximately 60,000 soundings) from the particularly for the prediction of supercells. lower 48 United States are evaluated. Cloud-to-ground The purpose of this study is to use rawinsonde data to lightning data and severe weather reports from Storm examine several parameters commonly used to forecast Data are used to categorize soundings as representative of severe thunderstorms and tornadoes. The research com- conditions for no thunder, general thunder, severe, signifi- plements work by Rasmussen (2003) and Rasmussen cant hail/wind, or significant tornado. Among the and Blanchard (1998), but includes a much larger dataset detailed calculations are comparisons between both con- (an order of magnitude larger), null cases, and does not vective available potential energy (CAPE) and lifted con- attempt to determine convective mode.
    [Show full text]