Deutscher Wetterdienst sites around Germany Hohenpeissenberg Meteorological Observatory ▲ The MOHp at a glance:

1 Information pavilion and entrance 8 Technical operations building (technical gases) 2 Balloon filling hall / sonde launch base 9 Office building with ozone laboratory 3 Brewer/Dobson measurement platform (RDCC) 10 Wind mast and relay station for disaster management 4 Aerosol lidar (RALPH) 11 Observation platform/radiation measurements 5 Measurement field 12 Office building with workshop and conference room 6 Ozone lidar 13 Office building with wet chemistry laboratory 7 Laboratory container (mobile deployment) 14 GAW laboratories with measuring platform 15 Radar tower with GAW balcony and webcams

Deutscher Wetterdienst – Weather and climate The DWD's observatories are models of success, from a single source which combine long-term observations with on-site The Deutscher Wetterdienst (DWD) has been scientific expertise. In combination, these improve the authoritative source of weather and climate our understanding of atmospheric processes and information in the Federal Republic of Germany their description in models. In the present era, human since it was established in 1952. The multitude activities are affecting the atmosphere and its com- of services which the DWD provides to all sectors of position to an extent which exceeds the bounds of the economy and society results from its statutory natural variability. One prominent example is the duty to inform and conduct research as laid down caused by humans as a result of in the 'Deutscher Wetterdienst Act'. The DWD is emissions. The DWD's observatory a public institution and, as a federal authority, is concept reflects its early understanding that directly accountable to the Federal Ministry of processes of change in the atmosphere are slow. Transport and Digital Infrastructure (BMVI). This also means that these must be recorded and scientifically analysed over a long period of time. The DWD's tasks cover areas as diverse as , warning management, the The Hohenpeissenberg Meteorological Observatory meteorological safeguarding of aviation and (MOHp) shipping, climate and environment consultancy, The Hohenpeissenberg Meteorological Observatory climate monitoring, monitoring of radioactivity is the world's oldest mountain with in the air and in precipitation, the acquisition continuous meteorological observations since 1781. and management of meteorological data through It owns the longest continuous temperature record of to representing Germany in international organ- all mountain weather stations. The first observations isations such as the World Meteorological were taken by Augustinian Canons from the nearby Organization (WMO). Rottenbuch monastery, using standardised methods devised by the Societas Meteorologica Palatina in With around 2,000 weather stations (both automatic Mannheim. Even after the monastery's secularisation and staffed) and measuring sites, the DWD operates one of the densest and most effiin wahr an climate observing networks in the world. At present, there are around 2,250 highly qualified people working for the DWD, from weather observers and meteorologists through to IT or administrative specialists.

The DWD observatories The DWD operates two research observatories: the Lindenberg Meteorological Observatory - Richard Assmann Observatory (MOL-RAO) in Brandenburg, which focuses on the physical structure of the atmosphere, and the Hohenpeissenberg Meteoro- logical Observatory (MOHp) in Upper Bavaria, which focuses on the chemical composition of the

atmosphere. ▲ Albin Schwaiger, observer at the MOHp from 1788 to 1796

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14 Technical operations building (technical gases) Office building with ozone laboratory 11 12 13 10 Wind mast and relay station for disaster management 9 Observation platform/radiation measurements 8 Office building with workshop and conference room Office building with wet chemistry laboratory 6 7 GAW laboratories with measuring platform

Radar tower with GAW balcony and webcams 5

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in 1803, the former monks, parish priests and village The most recent addition (since 2016) is the teachers continued taking observations, first on a greenhouse gas observing network in Germany voluntary and honorary basis, later drawing on the within the European Integrated Carbon Observation resources of the Bavarian Academy of Sciences. The System (ICOS). Since over 50 years meteorological mountain weather station became a meteorological observatories have been excellent places for observatory of DWD in 1952. long-term development of complex observation systems such as systems and their The temperature-record over almost 250 years shows improvement. MOHp is involved in a variety of the climate warming due to anthropogenic influence. scientific co-operations at national and international 50 years of ozone observations at the MOHp reveal the levels, for example in the Scientific Assessment of depletion of ozone by (CFCs) and Ozone Depletion, in the Copernicus Atmospheric a beginning recovery since 2000. In the same trad- Monitoring Service (CAMS) or in the European ition, changes in the atmospheric chemical composition Research InfraStructure for the observation of have been studied for more than 20 years within the Aerosols, Clouds and Trace gases (ACTRIS). Global Atmosphere Watch Programme (GAW).

▼ Extended measurement field

3 Global Atmosphere Watch (GAW) chemical aerosol parameters, ozone and aerosol pro- The Hohenpeissenberg Observatory is part of files and substances in precipitation. Data measured the World Meteorological Organization's Global at Hohenpeissenberg are available to researchers and Atmosphere Watch Programme (GAW) established the general public all around the world via Internet in 1989. The objectives of this programme are to databases. One of GAW's goals is to promote wider use improve our understanding of atmospheric pro- of these data in products and services. cesses and assess man-made changes to the atmos- phere for their relevance for climate, healthand The Hohenpeissenberg Meteorological Observatory ecosystems. Ozone profiles have been measured at receives worldwide recognition as an outstanding Hohenpeissenberg since the late 1960s, trace gases, GAW global station. This is particularly due to aerosol parameters and substances in precipitation its comprehensive measurement programme in all since 1995. These substances play key roles in GAW focal areas, its unique long-term monitoring atmospheric chemistry processes, such as ozone of radicals and free acids, which enables scientists and aerosol formation, , the greenhouse to study numerous chemical processes, and its inter- effect or atmospheric self-cleaning. Scientists from national calibration campaigns aiming to improve MOHp are actively involved in the development of the quality of measurements. international standards for consistent measurements, for example measurement guidelines for GAW, Trace gases as well as in the improvement of our understanding One of the observatory's main GAW tasks is long-term of processes and the evaluation of changes in monitoring of trace gases. These contribute to atmos- atmospheric composition. pheric composition at extremely low concentrations, but nonetheless have a huge influence on chemical MOHp provides data to GAW for more than 100 reactive processes, such as ground-level ozone and aerosol trace gases, greenhouse gases, physical, optical and formation or the self-cleaning of the atmosphere, as

▼ Profile measurement of trace gases with MAX-DOAS ▼ Hydrocarbon measurements with a gas chromatograph ▲ Sunrise at the world's oldest mountain observatory well as on the atmosphere's radiation balance and addressed. Ozone is formed from nitrogen oxides the greenhouseeffect. Organic trace gases, nitrogen and organic gases under the influence of intensive oxides, sulphur dioxide, carbon monoxide and dioxide solar radiation. Measurements made at Hohenpeissen- and others are not only produced during the combus- berg demonstrate a decline of the anthropogenic tion processes associated with traffi ad energ organic trace gases by about half in the last almost generation, they also originate from industrial and 20 years, while nitrogen oxides decreased only agricultural processes and evaporation. Vegetation, slightly. Levels of ozone also declined much less than oceans and volcanoes are natural sources. Man-made had been anticipated due to several reasons. One is emissions alter the composition of the atmosphere the high organic emissions from vegetation during and, as a result, climate and air quality. heatwaves, another is the increase in background ozone in the northern hemisphere due to rising The comprehensive trace gas and aerosol measure- emissions in Asia. Both facts are confirmed by meas- ments from MOHp are used to study the interactions urements taken at Hohenpeissenberg and other GAW between various trace gases as well as between trace stations. Local, regional and global effects can only gases and aerosols under varying meteorological be identified in a worldwide network such as GAW. conditions. For example, simultaneous measurements of nitrogen dioxide, sulphur dioxide and OH radicals New ground-based remote sensing instruments improve our understanding of the formation of nitric are tested and developed at MOHp to obtain an and sulphuric acid. These substances contribute to even broader picture of the atmospheric chemical aerosol formation and modify the ability of aerosols composition. One example is the MAX-DOAS (Multi to grow into cloud droplets, to be washed out (acid Axis Differential Optical Absorption) instrument. rain) and to reflect solar radiation (indirect aerosol This instrument is used for profile measurements, effect, climate effects). Questions concerning the for example of nitrogen dioxide, formaldehyde and formation of harmful, ground-level ozone are also aerosols.

▼ Inlets for trace gases and aerosols ▼ GAW laboratory

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▲ Measurement of chemical self-cleaning: OH radicals

Chemical self-cleaning For over 20 years, the Hohenpeissenberg Observa- tory has been the only station worldwide to monitor the chemical self-cleaning of the atmosphere on a continuous basis by means of long-term measure- ments of the hydroxyl (OH) radical, our most important 'atmospheric detergent' during daytime hours. OH radicals trigger the decomposition of pollutants from various sources and, in most cases, prevent pollutants building up in the atmosphere. These radicals catalyse chemical oxidation and transform pollutants into water-soluble substances. Only these can be washed out of the atmosphere by precipitation.

The amounts of highly reactive OH radicals are influenced by ozone, sunlight, water vapour and pollutants. Reactions with OH radicals do not only clean the air but also form degradation products, such as ground-level ozone, acid rain and aerosols, which can be harmful to health and environment. The unique long-term monitoring activities by MOHp improve our understanding of chemical and climate processes. This understanding is the basis for control and climate forecasts.

Monitoring of the ozone layer Ozone is a trace gas which is distributed over the 's entire atmosphere. More than 80 per cent of ozone reside in the stratospheric ozone layer, between 10 km and 50 km above the surface. Ozone is very important for our atmosphere: Ozone absorbs short-wave solar UV radiation, and the stratospheric ozone layer acts as 'natural sunglasses' which protect life on earth against excessive UV radiation and the dangers of, for example, sunburn and skin cancer. Ozone also influences the earth's radiation budget controlling climate and layering of the atmosphere. Ozone heats the stratosphere (10 km to 50 km) and is an important greenhouse gas in the troposphere (0 km to 10 km). Ozone is a highly reactive gas playing a key role in many chemical processes in the atmosphere, ▲ Top: Ion mass spectrometry such as the destruction of pollutants and chemical Centre: Quality assurance and calibration under laboratory conditions self-cleansing processes. at the SAPHIR Chamber, Jülich Research Centre Bottom: Laser mirror for stratospheric ozone measurements Near the surface of the earth, ozone is an aggressive oxidant that can affect health, plant growth, etc.

7 Ozone laser optics ▲

The 50-year Hohenpeissenberg ozone time series clearly show the impact of anthropogenic destruction of ozone by chlorofluorocarbons (CFCs). Thanks to the 1987 Montreal Protocol, production of ozone- depleting CFCs was phased out in the 1990s. These CFCs are now slowly disappearing from the earth's atmosphere and the ozone layer is beginning to recover. Full recovery of the ozone layer is not expected before the second half of the 21st century. By then, however, the entire atmosphere will change significantly due to increasing greenhouse gases and climate change. The troposphere will heat up and the stratospheric ozone layer will cool down. Ozone and temperature measurements at Hohenpeissenberg are necessary to monitor these developments in the future.

▲ Launch of a balloon-borne ozone sonde ▼ Ozone column measurement (Brewer)

With an extensive ozone measuring programme launched in 1967, the Hohenpeissenberg Meteoro- logical Observatory plays an important role in international monitoring of the ozone layer. A few times per week, balloon-borne electrochemical ozone sondes and laser radar instruments measure the ozone and temperature distribution from the earth's surface up to an altitude of 50 km. The thickness of the ozone layer (total column) is determined several times a day using Dobson and Brewer spectrom- eters. Additional instruments provide continuous measurements of ozone near the surface.

With this programme, MOHp contributes significantly to monitoring the ozone layer under international agreements (Vienna 1985, Montreal 1987). This includes collaboration on the calibration and quality assurance of global ground-based as well as -based ozone measurements (WMO Regional Dobson Calibration Centre for , RDCC, since 1999). Experts from MOHp represent Germany in international bodies and contribute to reports on the state of the global ozone layer. ▲ International ozone calibration centre

8 9 Set-up of sensor ▲ technology on ICOS measurement towers

ICOS network for long-lived greenhouse gases The increase in and other greenhouse gases alters the radiation balance of the atmosphere – and therefore the climate. Since 2016 MOHp has been monitoring long-lived greenhouse gases and their evolution within a national observation network that has been established as part of the European research infrastructure ‘Integrated Carbon Obser- vation System (ICOS)’. Long-term measurements of carbon dioxide (CO2), methane (CH4), carbon monoxide (CO) and nitrous oxide (N2O) are per- formed on high towers, mountains, at coastal sites as well as on ships. Apart from use for fundamental research on climate change, these data are needed to assess the success of mitigation policies aiming at reduced greenhouse gases emissions.

In Germany, measurements for the ICOS atmos- pheric observation network are performed at eight tall towers, such as the 149 m television tower at Hohenpeissenberg. The measured gas concentrations, together with meteorological information about the origin of the air masses, are used to determine the greenhouse gas budgets in Germany and Europe. For this it is crucial that the quality of the measure- ments of CO2 concentrations must be of an uncertainty of less than 0.03% – a real challenge for measurement technology and quality management.

All the data and the corresponding model calcu- lations are available to the public. Germany’s ICOS greenhouse gas observing network is one of the best equipped in Europe and, owing to its central location, the centerpiece of European ICOS measurements.

Aerosols Aerosols, i.e. solid or liquid particles which are sus- pended in the atmosphere, influence the radiation budget, the formation of clouds and precipitation and, as a result, the weather and climate. The health impact of aerosols in the biosphere depends on whether the particles are from artificial sources such as soot or have a natural origin, such as Saharan dust or sea salt. Within the GAW framework, data on aerosols in the atmosphere have been collected and

- ▲ Chemical aerosol mass spectrometer

10 evaluated at Hohenpeissenberg continuously of aerosol particles in the lower air layers. since 1995. Anthropogenic aerosols have declined Furthermore, the height distribution and long-range in the last 20 years. Air quality issues related to transport of aerosol-loaded air masses as well as aerosol are addressed at MOHp through research on their optical properties are determined with Raman their formation, distribution, physical and optical lidar and ceilometers, the latter being part of a characteristics and atmospheric residence time. network of about 150 stations in Germany. The measurements support and validate chemical High-accuracy Lidar measurements reach the weather forecasting, i.e. forecasts of concentrations stratosphere (up to 25 km) whereas the ceilometers of atmospheric trace gases and aerosols, under are able to detect clouds up to 15 km and aerosols the European Union's Copernicus Atmospheric in the troposphere. Atmospheric turbidity measure- Monitoring Service (CAMS). ments also record particles at even higher altitudes, where enhanced aerosol concentrations can be found Measurements at MOHp cover the number, mass, size, after severe volcanic eruptions, for example. turbidity characteristics and chemical composition

11 Research radar transmit and ▲ receive antenna

Research weather radar The weather radar research started at Hohen- peissenberg in 1968. At MOHp, DWD now operates a modern, third-generation research radar that is identical with the other 17 weather radars of DWD's radar network.

Weather radars continually scan the atmosphere and can detect precipitation within a radius of up to 180 km and up to 14 km altitude. The systems can distinguish between snow, hail and sleet (solid) as well as rain and drizzle (liquid).

The main tasks of the MOHp radar team are to: support the 24/7 routine measurements of DWD's radar network; operate the research radar; develop operational monitoring procedures for high quality radar data; verify new products such as quantitative ▲ Eruption of the Eyjafjallajökull volcano (2010) precipitation estimates; test new hardware components and radar operating software; Volcanic ash, Saharan dust and forest fire smoke test new signal processing techniques and radar The DWD’s volcanic ash evaluation centre is situated technologies; at the Hohenpeissenberg Meteorological Observa- support the introduction of radar-based tory. Eruptions of Iceland's Eyjafjallajökull (2010) techniques in weather forecasting; and Grimsvötn (2011) volcanoes transported tiny particles of ash of a few micrometres in diameter all the way to central Europe. High concentrations of volcanic ash are dangerous for aircrafts. Especially during the first event in 2010, air traffi ws stoppe across large areas for a lengthy period of time. Other long-range transports of aerosols –mainly Saharan dust or forest fire smoke – occur more frequently, but are mostly harmless owing to their composition or large dilution. Nonetheless, Saharan dust can have a significant influence on the weather (turbidity, cloud formation), on the production of solar energy and on health. Using the lidar systems, it can be distinguished between ash, dust and other aerosol types. These measurements can be used to determine continuously, under clear sky conditions, the concentration of volcanic ash over Germany and thereby provide valuable information for aviation- related decision-making.

12 operate additional measuring instruments to and modernisation of measurement programmes, safeguard the quality: ombrometers (for measuring concerted processing of scientific topics and the precipitation totals at high time resolution), visibility of the observatory. disdrometers (for measuring drop size distribution in rain) and a vertically measuring micro rain radar). Researchers of the observatory participates in research projects and measurement campaigns. The radar team builds on a thorough understanding Herein, the observatory serves as a research platform of the measuring technology which is a prerequisite to for atmospheric chemistry process studies and advance weather radar-based products within DWD. supports the development of measuring methods. Findings are usually presented in joint publications. Research programmes and projects In order to better meet the requirements arising The worldwide recognition of the observatory in the from the GAW programme and to ensure a broader science community is also apparent in the participation monitoring of the chemical composition of the of its scientists in expert and advisory boards, which atmosphere, the MOHp also takes part in other assess the state of our atmosphere and climate. international programmes, such as the Network for Those assessments influence new developments and the Detection of Atmospheric Composition Change directions in atmospheric research. (NDACC), the European Monitoring and Evaluation Programme (EMEP) and the Aerosols, Clouds and Trace gases Research InfraStructure (ACTRIS). The aim of such participations is to achieve improve- ments and synergies for the observatory as regards data use, quality management, standardisation of measurement and evaluation methods, extension

▲ Aerosol lidar

13 Historical milestones

2016 Launch of the 2014 Opening of the aerosol evaluation centre German ICOS for the monitoring of volcanic ash atmosphere ob- serving network for 2011 Opening of the greenhouse gases weather theme trails

2002 Launch of the severe weather warning 2000 2001 Inauguration of the system KONRAD (radar) new GAW global 1999 Opening of the station building WMO Regional Dobson Calibration Centre for Europe 1995 Start of chemical measurements as part of the GAW programme

1968 Implementation of 1967 Start of the operational ozone the first weather measurement programme radar for remote detection and measurement of precipitation

1952 Foundation of the Deutscher Wetterdienst and transformation of the Hohenpeissen- 1940 Relocation from berg weather station into a meteorological the vicarage to a observatory new building on the western side of the mountain 1900 summit

1878 Integration of the station in the newly established Central Bavarian Meteoro- logical Office in Munich 1809 Takeover of operational responsibility 1803 Confiscation of Rottenbuch monastery 1800 by Bavarian Academy of Sciences during the secularisation; continuation of measurements under private auspices 1781 Start of daily 1780 Foundation of a weather observa- meteorological tions according station as part of the to the rules of the station network of Societas Meteorolo- the Societas Meteo- gica Palatina in Mannheim rologica Palatina, funded by Duke Elector Karl Theodor 1758/ First meteorological observations 1759 1700

A detailed history of the Hohenpeissenberg Meteorological Observatory is available (in German) in: Peter Winkler: Hohenpeissenberg 1781–2006 – das älteste Bergobservatorium der Welt (The world's oldest mountain observatory). Geschichte der Meteorologie in Deutschland, Volume 7. Self-published by the Deutscher Wetterdienst, Offenbach 2006. (ISBN: 978-3-88148-415-2)

14 Hohenpeissenberg

Weather records Measurements Value Day/Month/Year

Annual mean temperature since 1781 6,3 °C

Highest temperature since 1879 33,8 °C 29.07.1947

Lowest temperature since 1879 -29,1 °C 11.02.1929

Warmest month since 1781 20,7 °C August 2003

Coldest month since 1781 -12,4 °C February 1956

Warmest year since 1781 8,9 °C 2015

Coldest year since 1781 4,2 °C 1829

Mean annual precipitation total since 1879 1209,7 mm

Highest 24-hour precipitation total since 1879 138,5 mm 21.05.1999

Highest monthly precipitation total since 1879 366,6 mm June 1979

Lowest monthly precipitation total since 1879 0,2 mm November 2011

Month with the most sunshine since 1937 332,3 hrs July 2006

Month with the least sunshine since 1937 30,7 hrs December 1947

Mean annual sunshine duration since 1937 1820,3 hrs

Strongest wind gust since 1939 176,4 km/h 27.11.1983

Highest snow depth since 1901 145,0 cm 10.03.1931

Highest 24-hour amount of new snow since 1948 48,0 cm 23.11.1972

Highest monthly amount of new snow since 1948 179,0 cm January 1968

Highest air pressure (station level) since 1781 927,7 hPa 15.08.1847

Lowest air pressure (station level) since 1781 862,6 hPa 02.12.1976

15 Imprint Deutscher Wetterdienst (DWD) Press and Public Relations Text and editing: Gertrud Nöth Texts: Meteorologisches Observatorium Hohenpeissenberg/ Gertrud Nöth Pictures: Helmut Bernhardt, Schongau, (cover image), Dr. Hartwig Harder (p. 12 Eyjafjallajökull), DWD Visit us on our Layout: Borgmann Grafikdesign website:

Deutscher Wetterdienst (DWD) Meteorologisches Observatorium Hohenpeissenberg Albin-Schwaiger-Weg 10 82383 Hohenpeissenberg Through our website at www.dwd.de Tel.: +49 (0) 69 / 80 62 - 97 10 you have also access to our pages on: Fax: +49 (0) 69 / 80 62 - 97 07 E-Mail: [email protected] www.dwd.de/mohp DWD 1st edition, 1 000 / 07.19