Climatological Characteristics and Radar Echo Analysis of Hail in Tangshan,Hebei

Based on the observation data at 11 stations from 1974 to 2009 in Tangshan and upper-air observation data from 1999 to 2009 and Doppler radar data of hail from 2006 to 2009,the spatial and temporal distributions and climate characteristics and radar echo features of the hail were analyzed.Using different analytical methods of mutation,we analyzed sudden changes of hail.The results show that the hail mainly occurs in mountainous and semi-mountainous areas north of Tangshan.The annual hail days reached the peak in the 1980s,and then show a decreasing trend from the 1990s.A sudden change spot of annual hail days occurred in the early 1990s.After the change spot,the annual hail days reduced obviously.The release of the strong instability energy will be conducive to the formation of hail in unstable region.The height of hail zero layer is at 3.4 km,the height of -20℃layer is at 6.3km.Most of the strong hail's radar echo centers are more than 60 dBz.The vertical sections are all characterized by slantwise echo structure. The top of echo is more than 8 km.The most vertical integrated liquid water content is more than 25 kg?m~(-2).There is a convergence feature on the basic radial velocity images.