A hailstorm occurring on May 9, 1999 in the Huanghuai region is studied by using the combined data from the precipitation radar （PR）, microwave imager （TMI）, and visible infrared scanner （VIRS） on the Tropical Rainfall Measuring Mission （TRMM） satellite. According to the 3 successive orbit observations of 4-hour duration from TRMM satellite, the evolutional characteristics of the precipitation structures as well as cloud top brightness temperature and microwave signatures of the precipitating cloud are comprehensively analyzed for hail-and rain-storm stage. The analysis results show that the precipitation process evolved gradually from the hail-precipitation in the early stage i.e. the hail-storm stage with strong convection, into the later stage, i.e. the rain-storm stage with weakening convection. In the early stage, there existed several strong convective cells in the hail-cloud, and there was so much solid precipitation in the middle-upper layer that the contribution of rainfall amount above the freezing-layer to the whole column precipitation amount is far greater than that within the melting-layer. However, in the rain-storm stage, the convective cells were surround by a vast stretch of stratiform clouds, and the height of precipitating layer was gradually reduced, the rainfall above the freezing-layer obviously reduced, and thus the contribution of rainfall amount within the melting-layer rapidly increased. Comparison of the contribution of the rainfall at different heights to the total column rainfall indicates that the larger the proportion of the rainfall above the freezing layer in the total column precipitation amount, the more intense the convection in the precipitating cloud. Inversely, the larger proportion of the rainfall within the melting layer means that the precipitating cloud is more stable （stratiform clouds）. The different response trends of microwave signatures to precipitation rate in different precipitation stages suggest that it is better to consider at first the str
Acta Meteorologica Sinica
973项目“空间微波遥感地海表和大气数据验证”（2001CB309402）.致谢：感谢NASA Goddard Distributed Active Archive Center提供TRMM卫星资料.
TRMM, Precipitation radar, Hailstorm, Precipitation structure, Microwave brightness temperature