CHARACTERISTICS AND RELATIONS OF LIGHTNING AND RADAR ECHOES FOR STRONG CONVECTIVE RAINSTORMS IN YUNNAN

Based on cloud-ground lightning data and Doppler weather radar echo products, both the characteristics and the relations of lightning and radar echoes for strong convective rainstorms over Yunnan are analyzed during the flood season of 2007. The results show that most rainstorms are convective in which lightning is mostly negative and the negative lightning number accounts for more than 90% of the total. Although the correlation between precipitation and the lightning number is small on the rainstorm day, the large day-lightning frequency usually produces heavy precipitation. Hourly evolution of precipitation and lightning frequency shows peak-style characteristics. And their evolution is very coherent in strong rainstorm, but lightning often occurs before precipitation, whose peaks are in phase with or 1-to-2-hour lagged behind that of lightning frequency. Meanwhile the peaks of positive frequency are in phase with or fall behind that of precipitation. When the wind field is heterogeneous in radial velocity, it is conducive to both the development of convection echoes and occurrence of lightning. Strong lightning-producing convective rainstorms correspond to strong echo fields and usually result in reflectivity above 30 dBZ and echo top ET of more than 9 km, respectively.