Mountains’ effects on weather being studied

Press, 2 March 1982, Page 18

Mountains’ effects on weather being studied

By

RALPH KAZARIAN

of the National Science

Foundation, Washington, D.C.

Scientists from the United States and' 12 other countries are preparing for a massive effort to study the complex wind patterns and atmospheric conditions of central and southern Europe to pave the way for better weather predictions in the area, which includes the Po Valley, the vital breadbasket of that region. The year-long project is sponsored by the World Meteorological Organisation (W.M.0.) of the United Nations and the International Council of Scientific Unions (1.C.5.U.). Scientists will concentrate on learning more about the critical role mountains play in creating vicious cyclones, severe winds, torrential rains and floods that annually plague large parts of Europe. Information gathered during the project could be useful in understanding how mountains affect weather and climate in other areas of. the world. One of the primary interests of United States scientists is to represent realistically mountains in computer models for weather prediction. This problem has been a major one for forecasters for a long time. United States scientists also are interested in studying the physical processes that cause winter storms downwind of mountain barriers. In the United States a major region of storm development is east of the Rocky Mountains. In Europe, the storms develop downwind of the Alps, causing devastating floods such as those which periodically have destroyed buildings and objects of art in Venice and Florence. - In addition, United States scientists are interested in questions & concerning s • local phenomena such as the des-

tructive Chinook winds of the; Rockies. Chinook winds in January gusted to 220 kms per hour, demolishing several homes and aircraft and toppling power poles in Colorado. The high winds were accompanied by a temperature increase of 10 degrees Celsius in half an hour. The American effort in the project — named ALPEX for Alpine Experiment — is being co-ordinated ,by the National Science Foundation (N.S.F.). which has issued grants totalling approximately $1 million : to 12 universities and research institutions to participate. Additional support is being pro- ; vided by the National Oceanic and Atmospheric Administration' (N.0.A.A.). Besides the United States, the participating countries include Belgium, Czechoslovakia, France, the Federal Republic of Germany, Hungary, Italy,. Poland, Romania, Switzerland, the U.S.S.R, and Yugoslavia. Researchers have limited information.. about how much mountain complexes such as . the Alps affect the weather and climate. It is known, however, that even r mountain complexes of moderate size influence the atmosphere, directly by deflecting and accelerating the wind flow and indirectly by providing elevated sources of heat. Mountains not only cause “drag" or slowing down of winds, but they also cause a phenomenon called blocking, a • situation in which the; normal . flow of .weather patterns are stopped, sometimes for weeks at a time; An understanding of these, and other, mountaincaused phenomena are crucial ' to the development of weather and climate models.

The Alps were selected' as the projects site because all phenomena caused by mountains are found in that region. In addition, the Mediterranean area south of the Alps has the highest frequency of cyclones in the Northern Hemisphere. Other reasons for. the site selection ' are the " size of the Alps and the fact that there are long records of continuous, meteorological observations, including excellent data from several summit observatories. . A twb;month Special Observing Period- (5.0. P. is taking place between March 1 and April 30, 1982. Less intense observations will continue until September 30,1982. The project will be headquartered in Geneva, Switzerland. Observations during the experiment will be made by systems of the World. Weather Watch and several special AL-PEX-de’dicated platforms such as ships, aircraft, balloons and radars. Two large aircraft being provided for ALPEX by the United States are an Electra operated by the National Centre for Atmospheric Research (N.C.A.R.) in Boulder, Colorado, and a P-3 operated by N.O.A.A. The polar-orbiting satellites,.including the geostationary Meteostat, will play a vital role in ALPEX. At the end of the 5.0. P., raw data from research aircraft will be preprocessed at individual flight facilities and then sent to the special ALPEX Data Centre for aircraft which has been established at N.C.A.R. A preliminary “quick look” data set is expected to be prepared within a few months after the end of the S.O.P. on April 30. The final data set will • be released 12 to 18 months later.