我国中东部3-9月云-地闪电密度和强度分布特征

DISTRIBUTION OF CLOUD-TO-GROUND LIGHTNING DENSITY AND INTENSITY DURING MARCH-SEPTEMBER OVER CENTRAL AND EASTERN CHINA

我国比较完整的云-地闪电(简称地闪)活动的气候规律研究尚较缺乏。基于我国国家雷电监测定位网2009—2013年3—9月地闪观测资料统计分析了我国中东部地闪密度和强度的时空分布和不同等级分布特征。结果表明:我国中东部总地闪密度空间分布同年平均雷暴日、卫星观测的闪电密度等的空间分布虽存在一些差异、但具有很大的相似性。我国中东部呈现3个显著的高地闪密度区和3个次高地闪密度区。总地闪密度候变化和日变化均为单峰型;总地闪日变化峰值为北京时间16时左右,正地闪峰值滞后总地闪约1小时;春季和上午时段正地闪占总地闪的比例较高。我国中东部99百分位的极端日总地闪密度、时总地闪密度、地闪强度分别为1.2次/(d×km^2)、0.8次/(h×km^2)、135.8 kA。总地闪高强度事件频率分布同正地闪高强度事件差异较大,大于39.1 kA的总地闪高强度事件发生次数最多的区域为珠江三角洲区域,而大于60.6 kA正地闪高强度事件发生次数最多的区域为四川东部。不同区域之间的日地闪密度和强度等级存在差异,长江中下游区域不同等级的日总地闪密度阈值最高;西南区域不同等级的总地闪强度阈值高于其他区域。研究结果为我国不同等级的雷电预报提供了气候统计基础。

Little work has been done on the climatological characteristics of cloud-to-ground lightning （ CG lightning） activity in China. Based on the observation data from National Lightning Detection Network of China （from March to September of 2009 -2013 ）, the spatial and temporal distributions are investigated of different grades of CG lightning density and intensity over central and eastern China （ C-E China）. The spatial distribution of total CG lightning over C-E China is similar to that of annual mean thunderstorm days and lightning den- sity observed from satellites, though with differences among them. For the spatial distribution, total CG density over C-E China appears to have three high density areas. Both the monthly and pentad variations of total CG lightning density have a single peak. The peak of total CG lightning appears at 16：00--17：00 （Beijing Time）, while the peak of positive CG lightning lags about 1 hour behind the total CG lightning. Daily total CG lightning density in C-E China reaches an extreme level of 99% at the value of 1.2 tl/（ d x km2 ）, 0.8 fl/（ h x km2 ） for hourly total CG lightning density and 135.8 kA for total CG lightning intensity. Spatial distribution of high total CG lightning intensity （ higher than the 4th grade, 〉 39.1 kA）, which mostly occurs in the Pearl River Delta region, differs much from high positive CG lightning intensity （higher than the 4th grade, 〉 60.6 kA）, which appears to be higher in the eastern Sichuan province. The grades of daily CG lightning density and intensity show some differences among different regions. The thresholds of different grades of daily total CG lightning den- sity over the middle and lower reaches of Yangtze River are the highest among the five areas; the thresholds of total different grades of CG lightning intensity over Southwest China are higher than those over the other four areas. These results could help us better understand the climatological characteristics of CG lightning in China.