A five-year climatological lightning characteristics of linear mesoscale convective systems over North China

摘要

The lightning characteristics of 89 linear mesoscale convective systems (MCSs) occurred over the Beijing area from the year of 2007 to 2011 were analyzed by lightning data and S-band radar information. According to different morphology of radar echo, linear MCSs were classified into six categories: leading convective lines with a trailing stratiform region (TS for short), leading stratiform region with a trailing convective region (LS), leading convective lines with no stratiform region (NS), bow echo of leading lines (BE), leading convective lines with a parallel stratiform region (PS), and broken line stratiform (BL). The results showed that linear MCSs occurred frequently over the Beijing area at the summer time, in particular, TS, LS and PS modes totally accounted for 73% of linear MCSs. On the average, lightning mainly concentrated in the linear convective region, and small amount of lightning occurred in the stratiform region. At the mature stage, lightning mainly located in the linear convective region with strong radar echo of TS, LS, and PS MCSs. At the dissipating stage, the lightning gradually increased in the stratiform region of TS MCSs, whereas fewer lightning occurred in the mode of LS MCSs, and positive cloud-to-ground (+CG) lightning accounted for a large percentage in the mode of PS MCSs. From the distribution of +CG/CG in three archetypes of linear MCSs, it is found that PS MCSs with highest the proportion of +CG/CG, and then followed by LS MCSs while the lowest ratio appeared in TS MCSs. The relationship between lightning frequency and volume of 40 dBZ radar echo exhibited linear correlation in three distinct archetypes of linear MCS. Environmental factors of linear MCSs exhibited that high CAPE (Convective Available Potential Energy) value and the larger wind shear of 0?6 km played an important role to sustain the convective development of TS, LS and PS MCSs.