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Inadvertent Weather Modification
The Urban Heat Island
The METROMEX project
St. Louis, MOhttp://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
From Changnon, et al., 1971
From Changnon, et al., 1971
From Changnon, et al., 1971
From Project METROMEX, 1974 (BAMS)
From Project METROMEX, 1974 (BAMS)
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)
From Project METROMEX, 1974 (BAMS)
From Project METROMEX, 1974 (BAMS)
From Project METROMEX, 1974 (BAMS)
From Project METROMEX, 1974 (BAMS)
From Project METROMEX, 1974 (BAMS)
From Project METROMEX, 1974 (BAMS)
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
