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Martin Hagen
Institut für Physik der Atmosphäre, DLR Oberpfaffenhofen, 82234 Weßling, Germany
Introduction
Weather radars are an essential information source for the monitoring of precipitation systems. However,
a single radar often can not observe the large area covered by those systems. Therefore, radars are
combined into radar networks. Several national and international radar networks are now available in
Europe. Although, standards for exchanging data have been defined during the COST 73 action
(Newsome, 1992), all the services use different scanning and data evaluation procedures. In addition, to
avoid abuse of real-time data, several restrictions limit the data exchange within Europe.
Although there are about 40 operational weather radars in the extended Alpine region, no readar
composite covering the Alps is available at the present time. The radar composites from France,
Switzerland, Germany and Austria are available either as national composites or combined international
composites. Recently efforts were undertaken to combine the data from several weather radars in
northern Italy into a radar composite (SINA composite, Crespi, 1999). The SINA composite will be
available for the MAP-SOP.
In the frame of the HERA project the radar networks from Switzerland, Germany and Austria where
combined to a North Alpine radar composite (Hagen et al., 1999). The North Alpine radar composite was
generated for 9 precipitation events lasting between 1 to 5 days. For one event (the South Ticino flash
flood) also data from French radars where included.
During the MAP-SOP an Alpine radar composite will be generated routinely consisting of data from
French, Swiss, German, Austrian and Italian radars.
Alpine Radar Composite
Weather radars in the extended Alpine region are operated by several national and regional agencies.
From the French radars the radars at Bourges, Lyon, Nancy, Nimes, Sembadel, Trappes and Troyes do
contribute to the Alpine region. All three Swiss radars at Albis, La Dôle and Monte Lema; and the four
Austrian radars at Feldkirch, Schwechat, Patscherkofel and Zirbiskogel are included into the composite.
From the German radars the radars at Neuheilenbach, Frankfurt, Neuhaus a.R., Eisberg, Türkheim and
München observe the southern part of Germany. The SINA composite will be generated from data of the
radars at S. Pietro Capofiume, Monte Grande, and Fassalon di Grado in a first step. In October 1999 the
new radar at Bric della Croce will be available. Furtheron radars in Pisa and Spino d’Adda are available.
Most of the French radars operate at S-band frequencies, all the others are C-band radars. Most of them
are Doppler radars, some of the Italian radars are polarimetric Doppler radars. The maximum range of
the radars is between 200 and 240 km.
Each radar data service provides a great variety of different products. However, only a few of these are
archived continuously or available for international exchange. These products have coarse quantization
steps and level changes at different values. Further more different Z-R relations are used for converting
measured reflectivity to rainfall rate. The Z-R relations are: Austria, Italy, and France Z = 200 R1.6,
Germany Z = 256 R1.42 and Switzerland Z = 316 R1.5. The Swiss and German Z-R relations are based on
local experience, the other one is taken from literature. Additionally, different scanning procedures, time
resolution, map projections, and calibration complicate the combination of different data sources.
For the Alpine radar composite an area of about 1450 by 950 km2 between 2 E to 18 E and 42 N to 50
N was selected. The horizontal resolution is between 2 x 2 and 4 x 4 km2, depending on the available
data sources. Due to the different map projections used by the services, the position error of the
precipitation cells is in the order of 2 to 4 km. Six rain rate levels are used: >0.3, >1.0, >3, >10, >30,
>100 mm/h. The map projection of the composite is a stereographic one with the reference point at 60
N and 10 E.
Figure 1 shows an example of the Alpine radar composite as it was generated for the HERA project. No
Italian radar data were available for this event.
Figure 1: Alpine Radar Composite for the South Ticino flash flood (HERA and MAP episode).
Generation of the Composite
In order to faciliate the compositing process national and international radar composites are used.
National composites are available from France, Switzerland, Germany, Italy (northern part only) and
Austria. An international radar composite is available from the Deutscher Wetterdienst. This composit
covers Germany, Denmark, Czech Rep., Austria, Switzerland and large parts of France. Also available as
data source is the CERAD composite (CERAD = Central European Radar Composite). Access to the data
is provided through the Deutscher Wetterdienst (Offenbach). Data from the SINA composite as well as
other Italian radars are accessed through direct connections.
The composite will be available through the MAP Data Centre at the Operation Centres in Innsbruck,
Milano and Chur every 30 minutes about 20 after the data have been taken.
Acknowledgement
The HERA project was in parts supported by the European Commission, Programme 'Environment and
Climate' under contract ENV4-CT96-0332. The provision of radar data by the Deutscher Wetterdienst,
Austro Control, Swiss Meteorological Institute, and Meteo France is gratefully acknowledged.
References
Crespi, M., Fabbo, R., Monai, M., Nanni, S., 1999: Contributions of SINA-METEONET weather radar
network to MAP. Poster presented at the MAP-Meeting 1999, Appenzell.
Hagen, M., Schiesser, H.-H., Dorninger, M., 1999: Monitoring of mesoscale precipitation systems in the
Alps and the northern Alpine foreland by radar and rain gauges. Meteorol. Atmos. Phys., in press.
Newsome, D.H., 1992: Weather Radar Networking. COST Project 73, Final report of the management
committee. Kluwer Academic Publishers, Dordrecht, 254 pp.