The Study On Hail Automatic Identification And Application

This article designs the hail detection algorithm with Doppler Weather Radar . First, the China's new generation weather radar systems and its main products are described. Second,, American WSR₈8D hail detection algorithm development process is introduced. And the latest hail detection algorithm is analyzed in details.The new hail detection algorithm is rebuilt by using the VC programming language and is tested with the radar and surface report data of 16 hailstorm cases. The results showed that the algorithm works as well as the new version of MetStar's products and make great progress in comparison with the old version of Metstar's products. Correct configuration of the 0℃ and-20℃ environmental temperature height help to improve detection performance. In addition, a method to reduce the high false alarm rate (FAR) by raising the reflectivity threshold is also discussed.By the detailed analysis of the violent hail storm in Anhui in May 27, 2002, the main steps of operational hail detection is described. We must first consider the stratification of the atmosphere, stability and water vapor content. Second, ,whether or not there has obvious hook echo, bounded weak echo regions and mesocyclone characteristics in radar echo,. Whether or not the underlying surface conditions are favorable for storm development. Finally, through the VIL value changes and reflectivity variation characteristics derive hail warnings.The future hail detection research directions is also proposed, including the continued improvement of the current hail detection algorithms to identify suitable threshold for the condition of our country., incorporation of storm top divergence and presence of mesocyclone as factors for hail detection as well as dual polarization radar to detect hail.