Meteorological Institute of Shaanxi Province
Meteorological satellites have provided useful information for improving weather forecasting, environmental monitoring and short-term climate prediction. In the field of weather forecast, it provides a more powerful means for the forecast of typhoon, rainstorm, hail, sandstorm and other severe weather. In this study, the microstructure of hail clouds were analysed by satellite observation data based on nearly a decade of hail events record of Shaanxi, Shandong, Guizhou, and Xinjiang. The comparison between the hail cloud and deep convective precipitation cloud characteristics which retrieved by polar orbit satellites shown different cloud properties such as cloud top temperature/effective radius, cloud glaciation temperatures. Based on the distinct cloud properties between hail clouds and convective clouds, we summarized the characteristics and further apply them on the FY-4A geo-stationary satellite which captures the life cycle of hail which happened on August 16, 2019, Shandong area. The results shown satellite has the potential to capture a hail cloud during its developing stage and use it as an application of early warning. The hail cloud shows the following characteristics: (1) There are significant differences in cloud physical characteristics between hail clouds and deep convective precipitation clouds. The cloud microphysical characteristics of hail clouds observed by satellites are shown in three aspects: Tg is cooler, with an average value of -33℃. The hail cloud reaches glaciation temperature with smaller effective radius (<40mm) with an average of 37.2?m when the clouds are fully glaciated. It also shows the smaller the re-g was, the stronger the hail cloud was. Additionally, hail clouds tops often have a reduction zone of re with increasing height. (2) All the studied areas have consistent cloud properties such as lower Tg, smaller re-g and decreased re at in comparison to adjacent convective clouds. However, it still showed regional variabilities which indicates we should establish different indicators for identifying hail clouds for early warming purpose. (3) The case study of FY-4A geo-stationary satellite shows geostationary satellite can track the evolution of hail clouds. By tracking the hail cloud, we found the geostationary satellite has a response consistent with that of the polar orbit satellite, providing a method for monitoring and early warning service of hail weather. The geostationary satellite can be used to track the development and evolution of the cloud cluster, at any time when the satellite detects strong hail signal because of the high time resolution. Combining satellite early warning with radar observation, the location of hail occurrence can be determined precisely. (4) Combining the indicators summarized by polar orbit satellites with FY-4 to track hail cloud evolution. Four hail storms occurred in Shaanxi and Shandong were applied for early warnings. Ground observations reported 22 hail events in the two regions, of which the satellite successfully warned 20 times in advance and missed two times. The average early warning time is about two hours before the hail disaster.