ENSO期间海洋性大陆典型地区闪电活动特征分析

Analysis of lightning activity over the typical marine mainland region during the ENSO

利用星载闪电探测器(光学瞬变探测器(OTD)和闪电成像传感器(LIS))的观测资料,配合其他气象资料,对厄尔尼诺期间(1998年春季)和拉尼娜期间(1999年春季)海洋性大陆典型地区(11.25°S—3.75°N,96.25°—128.75°E)的闪电活动变化特征进行研究,分析了雷暴单体数目以及雷暴单体闪电率对闪电活动变化的影响,并通过对比厄尔尼诺年春季和拉尼娜年春季的大气环流形势、相对湿度、最大对流有效位能、对流风暴高度等气象要素,讨论闪电活动变化的原因。结果表明:(1)从ENSO期间雷暴单体密度和闪电密度的空间分布变化特征来看,厄尔尼诺年春季的闪电活动及雷暴活动均比拉尼娜年春季的多,并且,从闪电数目和雷暴单体数目的纬向平均、经向平均的年际变化可以发现在厄尔尼诺年春季闪电活动、雷暴活动有东伸南移的趋势。(2)在海洋性大陆典型地区,雷暴单体数目的变化是闪电数目变化的主要因子,而雷暴单体闪电率的变化是闪电数目变化的次要因子。(3)与1999年春季相比,1998年春季的副热带高压范围大、强度大;地面相对湿度大,高空相对湿度小,上下层湿度差异大,有利于对流发展;对流风暴高度较高,冰相粒子层厚度也较深厚,对流发展旺盛;最大对流有效位能大于300 J/kg的天数的空间分布极大值区域正好与闪电密度、雷暴单体密度的大值区域对应,雷电活动与对流有效位能值密切相关。

The data from Optical Transient Detector （OTD） and Lightning Imaging Sensor （LIS）, witlq the other meteorological data, have been used to investigate the characteristics of lightning activity in the typical marine mainland region （11.25°S- 3.75°N,96.25° - 128.75°E） during the E1 Nifio （1998 spring） and during the La Nifia （1999 spring）. This study analyzes the impact of the number of the thunderstorm cells and the thunderstorm cell flash rate on lightning variation, and discusses the reason of lightning variation by comparing the atmospheric circulation, relative humidity, the maximum convective available potential energy and convective storm height between the E1 Nifio spring and the La Nifia spring. The results show that, （1） in 1998 spring, the number of lightning and thunderstorm cells is more than that in 1999 spring; and the zonal mean and meridional mean of thunderstorm cell numbers and lightning numbers show that there exists a trend of the lightning and thunderstorm activity being to the east and the south; （2） in the typical marine mainland region, changes in the number of thunderstorm cells are the major factors of lightning variation, and the thunderstorm cell flash rate is the secondary factors of lightning variation; and （3） compared with the spring of 1999, in 1998 spring the subtropical high＇s scope is bigger while the intensity is stronger; the relative humidity at the ground is bigger than that in the upper levels with a bigger difference of relative humidity between low and high levels, which is conducive to the development of convection; and, at the same time, the convective storm height is higher and the layer of ice phase particles is thicker with an exuberant convection development where the thunderstorm activity closely related with the CAPE value since the space distribution of the number of the days with the maximum CAPE greater than 300 J/kg is similar with that of the lightning density as well as the thunderstorm cell density.