In contrast to forecast parameters like temperature and pressure, the quality of the quantitative precipitation forecasts via numerical weather forecast models did barely progress during the past decade, although the physics of the forecast models was improved and the resolution increased continuously. But the forecast of precipitation is important for the public as well as for economy and administration, especially since extreme precipitation events could have big economical consequences (hailstorms, floods).

Therefore a wide measuring program “Convective and Orographical Induced Precipitation Study (COPS)” is planned in the context of the DFG priority program “Quantitative Precipitation Forecast” to get data and to develop procedures to improve quantitative precipitation forecasts via numerical models. COPS is conceived, accomplished and evaluated with the aid of the latest remote sensing and in-situ measurement techniques by the Institute for Physics and Meteorology (IPM) at Hohenheim University and the Institute for Meteorology and Climate Research (IMK) at the University of Karlsruhe and the Forschungszentrum Karlsruhe. A cooperation of the leading groups of researchers from Germany, other European countries and from the United States is aspired. The measuring activities of COPS will take place in summer 2007 in the low mountain range of southwestern Germany. The project is coordinated by Prof. Dr. Volker Wulfmeyer (IPM) and Prof. Dr. Christoph Kottmeier (IMK).

COPS will especially deal with the triggering of convection above complex terrain, because the main deficits of numerical models (e.g. the Local Model LM of the DWD) are the accurate forecast of events with high precipitation and their occurrence during the course of the day (see Figs.). Reasons for this behaviour of the model could be the resolution (grid spacing) and the convection parameterisation scheme as well as missing highly resolved data in space and time which decribe the inhomogeneity of humidity-, temperature- and wind-fields adequately. The measuring program should aid to correct this deficits and to improve the quantitative precipitation forecast.

COPS will analyse convective processes in different scales:

• Resolution of local convection above low mountain ranges (hot spots),
• Development of convection before and within frontal systems (squall lines) and
• Generation of convection by triggering of potential instability

If you would like to have more information or if you are interested in participating in COPS, please contact us (Prof. Dr. Ch. Kottmeier, Dr. U. Corsmeier). A booklet and a scientific document about CPOS will be released within a short time.

Precipitation forecasts for the northern Black Forest by LM-versions 7 km, 2.8 km and 1 km grid spacing compared with radar measurements. The 7 km-version is calculated unsing the LM convection parameterisation (Braun et al., 2003).

Difference between predicted and real precipitation in litres per m-2 during convective weather conditions (June 19, 2002). This forecast was calculated using the 7 km LM version with convection parameterisation (Eisenmann und Corsmeier, 2004).