2007年夏季长江流域及周边地区地闪时空分布及其天气学意义

Distribution and Spatio-temporal Variations of Cloud-to-Ground Lightning over the Yangtze River Basin and Adjacent Areas During the Summer of 2007

对2007年夏季(6—8月)我国长江流域及其周边地区(25°～38°N、100°～122°E,不包括甘肃、山东)地闪分布与不同区域的日变化特征进行了分析,并与同期雷暴日分布和FY-2C红外亮温(TBB)≤-52℃频率分布、低轨卫星8年观测的闪电分布及11年静止卫星TBB≤-52℃频率日变化进行对比,结果表明不同资料获得的对流活动时空分布具有很大的一致性。江淮流域、川渝、浙江西北部、武夷山中段的地闪活动较其周边区域明显比多年星载观测的闪电活跃。地闪活动7、8月较6月活跃且活跃区位置偏北,7月最为活跃的正地闪反映了该月长江中下游地区有较多中尺度对流系统发生发展。不同区域的地闪活动具有不同的日变化特征,江淮流域和川渝地区地闪日变化表现出多峰型特征,浙赣闽区域地闪活动的单峰型特征显著;其中江淮流域、浙赣闽区域的地闪活跃时段在午后,而川渝地区地闪活动夜发性显著;四川盆地西南部地闪呈现出明显的向东、向北传播特征;川西高原、云贵高原中部及浙闽丘陵沿海地区正、负地闪日变化差异较大。浙赣闽区域和川西高原地区正负地闪活跃时段基本一致,江淮流域、川渝地区和贵州地区负地闪活跃时段提前于正地闪,这几个区域的正地闪活跃时段都提前于TBB≤-52℃频率。这表明负地闪日变化特征较好地反映了初始深对流的日变化特征,而正地闪与TBB≤-52℃频率则较好地反映了成熟与消散阶段的深对流日变化特征。

Based on the June-August 2007 cloudtoground （CG） lightning dataset provided by the Meteorological Observation Center of China Meteorological Administration , the distribution and spatiotemporal variations of CG lightning over the Yangtze Riv er Basin and adjacent areas during the summer of 2007 are analyzed and compared wi th the thunderstorm distribution, the lightning distribution from loworbit sat ellites and with the deep convection distribution denoted by TBB≤-52°C. The re sults show that the four distributions are, to some extent, consistent with each other. By comparing the 2007 CG lightning distribution with the lightning distr ibution from the loworbit satellites, the CG lightning was more active over the Ya ngtzeHuaihe River Basin, Sichuan, Chongqing, the Northwest Zhejiang Province, t he middle of the Wuyi Mountains during the summer of 2007. In addition, the CG li ghtning was more active in July and August than in June, and the location of act ive areas is farther north, however, the positive CG lightning is the most active in July. It shows that the mesoscale convective systems occurred more often in July 2007. Diurnal variations of CG lightning were different over different area s. Over the Sichuan Basin and the YangtzeHuaihe River Basin, the diurnal varia tions of CG lightning had multiple active peaks, but there was only one active pe riod of CG lightning all day long over ZhejiangJiangxiFujian area. The CG light ning was often more active in the afternoon over the YangtzeHuaihe River Basin and ZhejiangJiangxiFujian area, but it had an obvious nocturnal feature over the Sichuan Basin. In the Southwest Sichuan Basin, the CG lightning obviously pro pagated eastwards and northwards. It is also found that there is a marked differe nce between the diurnal variations of positive CG lightning and negative CG ligh tning over the western Sichuan Plateau, the middle YunnanGuizhou Plateau and t he coastal areas in Zhejiang. By comparing the diurnal variations of negative CG lightning with the positive CG lightning and the frequency of TBB≤-52℃ from the F Y-2C satellite, the active period of negative CG lightning was often ahead of t hat of positive CG lightning and the active period of positive CG lightning in t hose areas was ahead of the frequency of TBB≤-52℃. It implies that the diurnal variations of negative CG lightning reflected the diurnal variations of initial convection, and positive CG lightning and the frequency of TBB≤-52℃ reflected the diurnal variations of mature and dissipating convections.