Analysis on Identifying Indexes of Hail Weather Process in Akesu of the Southern Xinjiang

Based on the routine meteorological data and CINRAD /CC Doppler radar products,the characteristics of environment conditions and radar echoes for 34 hail weather processes from 2009 to 2012 were analyzed and summarized in Akesu of the southern Xinjiang. The results showed that the hail weather would be much more likely to occur when the temperature difference between 850 hPa and 500 hPa was more than 30 ℃ and the dew point temperature was more than 10. 2 ℃ before the hail happened. CAPE index was effective on forecasting the hail when the diameter of hail was more than 10 mm,but it was limited to small- scale local hail weather. The weaker vertical wind shear from ground to 6 km height should also form hail. In additional,the suitable height of 0 ℃ layer and- 20℃ layer were propitious to formation of hail weather. The radar echo characteristics of hail cloud were as follows: The composite reflectivity factor was more than 50 dBZ,the radial velocity field was often accompanied with the adverse wind area,and the portion of hail weather processes appeared storm top divergence feature. The 45 dBZ strong echo height was more than 9 km,and the vertical section had echo characteristics of hail weather such as overhang echo,vault echo etc. The top height of hail cloud exceeded 12 km from June to August,and that exceeded 11 km in May and September. The threshold of vertical integrated liquid content was 18 kg·m- 2in May and 30 kg·m- 2in other months. The solid big triangle label appeared continually at least 5 volume scans in hail index products.