Weather chaos over the Rhine and Black Forest

Interim results of the weather research program COPS submitted

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The weather reality across the Rhine and Black Forest is much more complex than the computer models make predictable: this is the first report of the scientists at the halfway point of the world's largest research project on COPS (Convective and Orographically-induced Precipitation Study).

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Researchers from eight nations want to improve the weather forecast and enable climate models on a local scale with the help of nine research aircraft and a research zeppelins.

"Until now, research has assumed that landscapes like the Rhine Valley allow the air to flow through it like in a large canal. The computer models for forecasting the weather are correspondingly simplified, "said Professor Volker Wulfmeyer from the Institute of Physics and Meteorology at the University of Hohenheim as the first chairman of the COPS Steering Committee at yesterday's press conference at Baden-Airpark.

Too much simplification, which leaves precipitation forecasts locally up to 100 percent off, as the researchers from eight nations found out thanks to a phalanx of state-of-the-art measuring instruments from all over the world: "Since July 1, 2007, we measure for the first time three-dimensionally and with unprecedented accuracy Invisible parameters such as wind and moisture or particle distribution, which control rain formation, "explains Professor Christoph Kottmeier from the Institute of Meteorology and Climate Research of the Forschungszentrum Karlsruhe and the University of Karlsruhe. display

Complex vortexes and currents

The researchers documented complex flow conditions in the atmosphere, where air masses flow together, create vortexes and ascend to form thunderstorms. As a cause, the researchers suspect different warming of the soil surface, as they can be triggered by clouds, various substrates or in-homogeneities in the wind. "So far, we had to rely on assumptions - now we can see what's really going on and end the blind flight in the weather forecast, " says Kottmeier.

The goal of the scientists is a new generation of computer models that enables a truly accurate prediction at the level of individual districts. For this purpose, the researchers use their new measurement results almost in real time in the existing models and check the results of the calculations with new accuracy in reality in order to eliminate concept errors in the software piece by piece. "In the western part of the Black Forest, for example, only half as much rain falls as predicted, in the eastern part it is twice as much. That is, on a large scale, the computer models are correct, but in detail, the weather map often consists of areas with systematic errors, "Wulfmeyer cited an example.

High-tech at over 100 locations

To clean up the systematic mistakes, the scientists covered the Black Forest across the Rhine Valley to the Vosges with a network of more than 100 weather stations. In addition, there are five so-called super sites with a particularly elaborate device. Every five minutes, Europe's weather satellite Meteosat transmits live recordings. Also unique is the fleet of ten flying research platforms including a zeppelin, which scientists from Germany, France and Great Britain concentrated on Baden-Airpark.

"At every storm, there are particularly sensitive regions that we can only reach by plane, " emphasized COPS project partner Christian Keil of the German Aerospace Center (DLR). Depending on the weather conditions, these sensitive regions are located several hundred kilometers upstream, for example via Spain and the Bay of Biscay. With the help of additional airborne observations of the wind and the humidity, the understanding and the prediction of strong convection should be improved.

Flight into the eye of the storm

"Through international cooperation, we have a highly specialized fleet for the COPS project for the first time, " said Keil. For example, the German Falcon is in a position to make three-dimensional measurements from eleven kilometers up to the ground and thus examine the entire troposphere, in which the weather is happening, all at once. The British FAAM BAe 146 flies right into the eye of the storm and partially kills the thunderstorms in their early stages over the Atlantic, in order to continue their development to the Black Forest.

"If we had measurement results like these years ago, for example, Sturm Lothar would not have hit us so unprepared, " explained Wulfmeyer. "With COPS, we provide basic research that should better prepare us for extreme weather events such as floods and storms. At the same time, the weather models are the basis for the climate forecast - because how do we prepare ourselves for climate change in 30 years, if we have problems to predict the weather of tomorrow in detail, "added Kottmeier.

Project COPS

The COPS measurement campaign is part of the United Nations World Weather Research Program: World Weather Research Program of the World Meteorological Organization. Almost all of the approximately 20 meteorological institutions in Germany and the leading research centers for meteorology from France, Great Britain, Italy, the Netherlands, Austria, Switzerland and the USA are involved. The COPS measurement campaign is part of the Priority Program 1167 "Quantitative Precipitation Forecast" of the German Research Foundation (DFG) and is coordinated with the TRACKS measurement program of the Helmholtz Association of German Research Centers and the World Weather Research Program Forecast Demonstration Project D-PHASE.

An important measurement station at COPS is the US Atmospheric Radiation Measurement Program (ARM) Mobile Facility (AMF). The measurement campaign is embedded in a European one-year observation period, the General Observations Period (GOP).

(idw University Hohenheim, 20.07.2007 - DLO)