TRMM-Based Study of Lightning Activity and Its Relationship with Precipitation Structure of a Squall Line in South China

The data from precipitation radar (PR), lightning imaging sensor (LIS), and passive microwave imaging (TMI) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite have been used to investigate lightning activity and its relationship with precipitation structure of a strong squall line over south China on May 6, 2005. The results show that convective rains only occupied half of the area of stratiform rains, but the former contributed much more rainfall to the total than the latter. Most lightning flashes occur near the strong convective region, and a few flashes occur in the stratiform region of the squall line. At 6-km altitude, most of lightning flashes occur in the echo region between 35 and 50 dBZ, which peak during 40－45 dBZ, and fewer flashes can be seen in the echo region with reflectivity smaller than 30 dBZ. The results also indicate that the vertical profile of the maximum radar reflectivity has capability to reveal flash rate and vertical development of convective cells. Furthermore, it is found that most of lightning flashes occur in the region of low brightness temperature, especially the region lower than 200 K, and a few flash can also be seen in the region of 240－260 K, which usually corresponds to the stratiform region of squall lines. A combined study with another squall line over the Huanghe River－Huaihe River area on April 17, 2003 shows that there is a close relationship between flash rate and ice precipitation content between 7－11 km altitude at a convective cell scale, and the correlation coefficient is 0.92, which suggest that the stable relationship between flash rate and ice precipitation content can be valuable in the study of both the assimilation of lightning data into mesoscale models and lightning flash parameterizations of squall lines.