利用三维雷暴云动力—电耦合数值模式,通过对青海东北部地区2011年7月29日一次雷暴发展过程进行研究模拟,分析了青海东北部地区雷暴的电荷结构演变特征并从微物理方面讨论了其过程主要形成原因.结果表明,对流过程中霰粒子比含水量分布广,雹粒子比较少,以液态降水为主.青海地区雷暴以三极性结构为主,在上升气流比较弱时电荷结构呈现出下正中负的电荷结构,结构整体电荷密度分布较低,底部正电荷区与负电荷区深厚,霰粒子在下荷正电,冰晶在上荷正电.随着上升气流增大,冰晶粒子随着上升气流抬升碰并时荷正电在负电荷区上形成比较强的正电荷区,中部负电荷区主要是由霰粒子所携带负电荷形成,霰分布广且贴近地面,霰粒子在较低地方主要荷正电荷形成下部弱的正电荷区,随着降水过程拖拽霰粒子下部正电荷区消失,此时霰粒子对下部弱正电荷区形成起着重要作用.

In order to make up for the limitation of thunderstorm processes observation, and to explain the relationship between the large lower positive charge region（LPCC） and the warm cloud depth（WCD） of thunderstorms from the close relationship between dynamics, microphysics and electrification process over Tibet Plateau, sensitivity test groups are set in this paper. The sounding initial field of a thunderstorm process with obvious LPCC and strong convection in Naqu area of Qinghai-Xizang Plateau is changed by three ways, and 10 groups of initial field examples with different WCD are obtained. The possible relationship between WCD and LPCC is simulated and analyzed by using a three-dimensional dynamics-electrification coupled model. The results show that WCD is not the only factor determining the strength of LPCC in the Tibet Plateau. The obvious LPCC requires a thin WCD with strong but not too strong rising speed. Even if the WCD is very thin, too strong updraft is only easy to form a normal type thunderstorm with very strong main positive and middle negative charge areas, and too weak updraft is only form normal type thunderstorms with weak main positive and middle negative charge regions. The two main sources of raindrops, namely, raindrops collision and collection with cloud water and graupel melting to form rainwater, and the main source of graupel, namely, graupel riming with cloud water mainly depend on the convective intensity. The inhibition effect of thin WCD on warm cloud precipitation process is less than the enhancement of strong updraft on warm cloud precipitation process. When the convective intensity changes little, WCD mainly dominate the distribution height of ice particles. The thinner the WCD, the smaller the size and the more the number of cloud droplets is transported above 0 ℃. It is more conducive to the growth of low-level ice particles, and the more obvious LPCC and middle negative charge region.When WCD is thicker, it is more conducive to the growth of higher ice particles, and LPCC tends to weaken, while the middle negative and main positive charge regions tend to be obvious.

To gain further insight into the characteristics of lightning activity during the whole life of a tropical cyclone（TC）, World Wide Lightning Location Network（WWLLN） data, TC best-track data from the National Meteorological Center of China Meteorological Administration, black body temperature data from the Fengyun-4A satellite, and ERA5reanalysis data are used to explore typhoon Mangkhut, the strongest typhoon that landed in China in 2018. The temporal and spatial distributions of lightning activity and its variation with intensity during the whole life of typhoon Mangkhut are studied, as well as the relationship between lightning activity and wind circle radius and the underlying surface.Results show（1） the three-circle structure of the lightning activity in Mangkhut: the highest density of lightning in the inner core, almost no lightning in the inner rainbands, and the largest amount of lightning in the outer rainbands. The inner core lightning has a different main occurrence time from the outer rainband lightning, which can also produce a large amount of lightning in the open sea.（2） The azimuthal distribution of lightning activity is closely related to TC intensity,geographical location, and environment and is different in different periods.（3） There is no clear relationship between lightning activity and wind circle radius. The lightning activity mostly occurs in the southeast and southwest, where the wind circle has a smaller radius.（4） During and around TC rapid intensification, the inner core lightning activity has a certain indicator effect on TC intensity intensification. Moreover, there is a good correlation between lightning activity and convective intensity in the inner core.（5） The existence of islands and land plays an important role in severe convection development. When the stream hits a higher terrain, it is forced to lift, forming lightning. The southwest direction of the TC is about 300km away from the southeast side of the island, and sufficient water vapor, heat, and more anthropogenic aerosols are observed, which are conducive to updraft development, thus generating lightning. These insights contribute to the application of lightning data in monitoring and early warning of mesoscale and small-scale severe convections in TCs.

Based on LIS / OTD gridded lightning climatology data, ERA5 reanalysis data, and MODIS atmosphere monthly global products, we examined latitudinal and daily variations of lightning activity over land, offshore areas, open sea, and all marine areas (i.e., the aggregate of open sea and offshore areas) for different seasons over the Pacific Ocean and the adjacent land areas at 65 degrees N-50 degrees S, 99 degrees E-78 degrees W, and analysed the relationships of lightning activity with CAPE (Convective Available Potential Energy) and AOD (Aerosol Optical Depth). At any given latitude, the lightning density is the highest over land, followed by offshore areas, all marine areas and the open sea in sequence. The lightning density over land is approximately an order of magnitude greater than that over all marine areas. Lightning activity over land, offshore areas, open sea, and all marine areas varies with season. The diurnal variation of lightning density over land has a single-peak pattern. Over the offshore area, open sea, and all marine areas, lightning densities have two maxima per day. The magnitude of the daily variation in mean lightning density is the largest over land and the smallest over the open sea. The lightning density over the Pacific Ocean and adjacent land areas is significantly and positively correlated with CAPE. The correlation is the strongest over land and the weakest over the open sea. Cloud Base Height (CBH) may affect the efficiency of CAPE conversion to updraft. CAPE has a positive effect on lightning activity and has a greater impact on land than on the ocean. Over the sea, both CAPE and AOD can contribute to lightning activity, but the magnitudes of the influence of CAPE and AOD on lightning activity remain to be determined. Lightning activity over land and sea is a result of the combined action of AOD and CAPE.

为了认识以暖云强降水为主导的对流单体中的电荷结构特征及其形成原因,利用加入了起放电参数化方案的WRF模式,模拟了2017年5月7日广州局地突发的以暖云降水为主导的特大暴雨过程,分析讨论了此次过程中一个单体成熟发展阶段的电荷结构的特征及其成因.结果 表明,此次以暖云降水为主导的特大暴雨过程中的单体对流强度较弱,云顶高度低于同地区典型对流过程,强回波区由大雨滴形成,范围较小,顶较低,对流运动向0℃层以上输送的过冷水较少,不利于冰相粒子形成,导致大小冰相粒子含量均较少,其中含量最多的冰相粒子为雪花,其次依次为霰、冰晶、冰雹.云内起电较弱,以非感应起电为主.非感应起电主要以对流区中-15 ℃层以下正的起电率为主,感应起电率以对流区中的负极性为主.对流区中空间净电荷呈三极性结构,其中中部负电荷区和底部正电荷区中心电荷密度及电荷区范围相当,上部正电荷区相对较弱,范围较小.对流区外围仅有弱的中部负电荷区和底部正电荷区.中部负电荷区由带负电荷的冰晶和雪花共同主导,上部正电荷区由带正电荷的雪花主导,底部正电荷区主要是由带正电荷的霰粒子及带正电荷的雨滴主导.强起电区和放电区重合,主要集中在回波中心上部35～50 dBZ的对流区.