Comparative Analysis on Weather Characteristics and Convective Parameters of Torrential Rain and Hail in Yangtze River Delta

Based on the meteorological data recorded from 1971 to 2006,and the precipitation data during 1999—2009 in Jiangsu Province,Zhejiang Province and Shanghai,temporal and spatial distributions of severe convective weather are analyzed.The composite conceptual pattern of regional hail and rainfall events above 100 mm·(3 h)~(-1) caused by the North China cold vortex is also analyzed.Several physical parameters of the two kinds of convective weathers are calculated as well.Results show that the frequency of hail storm has a decreasing trend in the 30 years from 1971 to 2001 but a slight increase trend in the later 5 years.Hail and heavy rainfall events take place most in north of Jiangsu Province.The cold vortex is much stronger and lies further north in hailstorm than that in convective rainstorm weather.The high-level jet lies north in torrential rain weather,and in hailstorm it lies right underneath the hail-hit area.Moist tongue is often found at low level in the both weather conditions and dry tongue lies right above the wet area in high level during hailstorm while in torrential rain it is not.Statistics indicate that the 0℃height,the temperature difference between 500 hPa and 850 hPa,K index,precipitable water,and high-level wind shear,etc.can distinguish the category of the rainstorm and hailstorm well and the differences between them are—1700 m,7℃,8℃,—37 mm and 1.63×l0~(-3)s~(-1) respectively.