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Inadvertent Weather Modification. The Urban Heat Island. The METROMEX project St. Louis, MO. http://www.arrakeen.ch/usaaug98/110%20%20St.Louis.JPG. The Urban Heat Island. Produced by the combined effects of Heat Capacity Albedo Heat Generation Radiative Heating and Cooling Rates
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Inadvertent Weather Modification The Urban Heat Island The METROMEX project St. Louis, MO http://www.arrakeen.ch/usaaug98/110%20%20St.Louis.JPG
The Urban Heat Island • Produced by the combined effects of • Heat Capacity • Albedo • Heat Generation • Radiative Heating and Cooling Rates • Surface Roughness • Is this really weather modification?!
METROMEX • Metropolitan Meteorological Experiment • Studied the areas around St. Louis in the summers of 1971-1975 • Goals: • Identify effects of urbanization on atmospheric behavior (i.e. precipitation and severe weather • Identify physical process through which observed effects are produced • Identify the factors of urbanization which cause these effects
1. For cells originating in the St. Louis urban area, rainfall volume average was 216% greater than control sample. 2. For cells originating in the Alton-Wood River urban area, rainfall average was 289% greater than contral sample. 3. Convective initiation zones was more likely to found in the industrial areas From Project METROMEX, 1974 (BAMS)
Summary • Large Industrial/Urban areas favor • Higher temperatures • Increased rainfall downwind • Increased hailfall downwind • Differing microphysical precipitation process downwind • Higher convective cloud bases due to increased boundary layer height