Research on the Correlation Between FY-4A Satellite Cloud Parameters and Precipitation in Summer in Zhejiang Province
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Abstract:
Based on the cloud products from FY-4A Satellite and the raindrop spectrometer data in Zhejiang Province, this paper analyzes the characteristics of summer precipitation and its relationship with cloud parameters from 2020 to 2022. The results show that, according to the precipitation intensity, the occurrence frequency of moderate rainfall is the highest in summer in Zhejiang, torrential rainfall mostly occurs in the mountainous areas of southern Zhejiang, and the occurrence frequency of convective cloud precipitation in this area is also the highest. The relationship between precipitation characteristics and cloud parameters is manifested as follows. The occurence frequency of light rainfall is the highest for water cloud and cirrus cloud, supercooled water cloud and mixed cloud tend to result in moderate to heavy rainfall, ice cloud has the highest occurence frequency to produce heavy rainfall, particularly torrential rainfall and overlap cloud has similar precipitation features to water cloud. The average precipitation intensity increases with the decrease of cloud top temperature (CTT) and with the increase of cloud optical thickness (COT), but its correlation with cloud effective particle radius (CER) is not significant in this study. The combination of two parameters (CTT and COT) demonstrates the gradient variation of precipitation intensity and its higher sensitivity to COT, with heavy precipitation more likely to occur under low CTT and high COT. Incorporating CER to construct a three-parameter combination further reflects the effect of cloud droplet coalescence efficiency on precipitation microphysical processes, leading to more precise precipitation estimation. Convective cloud precipitation has the characteristics of lower CTT and higher COT compared with stratiform precipitation, but the stratiform precipitation is often accompanied by convective processes.