Comprehensive Observation and Analysis of an Artificial Rainfall Operation in Convective Stratiform Mixed Clouds
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Abstract:
Using Doppler radar data, the retrieved cloud parameters from FY 2E geostationary satellite, the retrieved products of MODIS polar orbiting satellites, and conventional precipitation data, the precipitation structure and catalytic effect of the stratus cumulus mixed clouds in a precipitation enhancement operation in Hunan on 17 August 2013 are analyzed. The results show: the clouds in the operation were mainly stratus cumulus mixed clouds with low cloud top temperature; above the -10 ℃ level, there was a deep ice phase growth zone and there were mainly ice phase particles at the cloud tops; beneath the -10 ℃ level, both cloud condensation coalescence and ice phase process were significant. Optical thickness and surface rainfall were correlated positively, reflecting well the area of precipitation. The vertical profiles of echoes show that the cold catalyzed layer had thicker thickness; there was abundant liquid water around the 0 ℃ layer; precipitation was produced by ice phase processes. For the configuration of the deep ice layer and the mixed layer was favorable to the occurrence of precipitation, catalysis operation was conducted in the area where precipitation formed in the cold cloud process, which is more scientific and reasonable. Physical statistical analysis indicates that the echo intensity at upper levels enhanced first after catalysis, and there was a lag at the lower levels, which means that catalysis induced raindrop growth first, and then the falling of the raindrop grown raindrops resulted in the enhancement of echoes at lower levels. Relative to the contrast region, catalysis can increase echo intensity,e.g., precipitation; relative to the prolonged life span of the target cloud area, the catalytic effect was more apparent.