Abstract:

To understand the evolution characteristics and cloud physical mechanism of lightning for hail and heavy rain clouds, using VLF/LF three-dimensional lightning monitoring data, combined with S-band dual polarization radar and ground observation data, statistical and comparative analysis methods were used to analyze the characteristics of individual lightning for 31 hails and 32 short-term heavy rains.The characteristics of single lightning, dual polarization radar echo and the correlation between lightning and convective development height were analyzed and compared in detail.The results show that more than two-thirds of the hail samples with lightning frequency are more than 50 times/6 min before hails fall.The ratio of positive ground lightning and positive cloud lightning of a hail monomer is high, while that of mostly heavy precipitation monomer is very low.The peak value of lightning frequency of 80% individual hail is 2~25 minutes ahead of the time of hails fall.The total lightning frequency of most individual hail rises sharply before hails fall, and the increasing rate of frequency is more than 4 times/min.The peak value of single lightning frequency is 2~35 minutes ahead of the precipitation peak value in more than half of the heavy rainfall, and the lightning frequency increases before the precipitation peak value in most single precipitation, and the increasing rate of lightning frequency is mostly below 4 times/min.The cloud flash frequency of the two types of monomers in the mature stage is the highest among the three stages.The cloud flash in the three stages is concentrated in the layer of 2~6 km height.In the hail monomer, the lower layer below the melting layer is composed of hail and heavy rain particles, and the upper layer is composed of hail and graupel.In the heavy rain monomer, the lower layer below the melting layer is composed of heavy rain particles, and the upper layer is composed of ice crystals and supercooled water droplets.The higher the convective height is, the more obvious the ice phase process is and the stronger the lightning activity is.In this study, lightning data and dual polarization radar parameters were combined to provide a reference for the identification and early warning of different types of severe convective weather and lightning.

Key words: Lightning frequency, Short-term heavy rainfall, 3D lightning