Analysis of a hailstorm event in the middle Yangtze River basin using ground microwave radiometers

A hailstorm event in the middle basin of the Yangtze River on 12 April 2010 is observed by the ground microwave radiometer located at Xianning, Hubei Province, China. The results show: (1) In the hail cloud very strong the updraft caused volatility of the cloud base height, while continuous upward transport of low-level air sensible heat and latent heat lead isotherms to upward lifting, with the other processes associated with the Bergeron effect and ice crystal depletion. Because of these macro and micro processes， the integrated water vapor and integrated liquid water content experinced continuous decline or rise, resulting in a multi-peak structure. (2) It is clear that, in the 4.2-8 km supercooled layer of hail cloud, dynamic exchange among water solid, liquid and vapor phases is very complex during the period of 08:40-13:00 UTC, characterized by alternating among droplet-ice depletion, Bergeron process and droplet-ice growth, causing an area of relative humidity less than 80% below 6 km with the liquid water content large value area of 0.7-1.8 g/m3 occuring in the height of 4.2-8 km, which results in forming the hail growth environment of alternating between wet and dry growth, conducive to the hail particles rapid accumulation and growth in stratified groups. (3) Using the microwave radiometer data to calculate the four instability indices MKI, KI, TT and HI, we find these indicators have a good indication to severe convective weather, and show a potential to severe weather nowcasting. If KI ≥38 is selected as early warning indicators of severe convective weather in the region, early warning can be issued 45 min ahead for the first hail severe convective weather, and it can issue early warning of the 2nd, 3rd, 4th convective cell that will impact the region, 20 min, 40 min and 42 min ahead of time, respectively.