摘要
利用NCEP、地闪、云图和WRF模式等资料,分析总结2010年8月11-12日和2011年8月15-16日关中近10年地闪次数最多的两次湿雷暴天气特征。结果表明:欧亚中高纬为两槽一脊环流形势,西太平洋副热带高压(下称西太副高)稳定少动控制陕西,关中低层受切变线直接影响,有利于盛夏强湿雷暴发生。北部高层冷平流和正湿位涡向南下滑,陕北能量锋区南压,陕西西南部低层暖舌向东北方向伸展,关中不稳定层结加强,最大对流有效位能超过3 000 J·kg-1,垂直上升运动深厚,是强湿雷暴发生的有利环境条件。西太副高偏强偏西,"上干下湿"层结不稳定,近地层高温高湿,对流有效位能偏大,垂直上升运动中心和对流云顶偏高,导致强湿雷暴比普通暴雨过程地闪明显偏多。关中地闪与强降水二者中心接近,密集区与低层高位温区走向一致,主要分布在50 m-2·s-2以下正螺旋度区。强湿雷暴不同阶段对流云团与地闪分布差异明显。发展阶段,MCS冷云罩显著扩大,北侧TBB大梯度区呈反气旋北凸,对流云顶和地闪密集区不一致,地闪趋于集中、频次增大;成熟阶段,TBB中心降至-76℃以下,地闪密集区与对流云顶基本重合,密度和频次达到过程最大,正闪分散在负闪密集区西南方向;消散阶段,地闪密集区与云顶逐渐分离,明显减弱、分散,正闪相对活跃。WRF输出的-20^-10℃层之间雪、霰粒子质量混合比与地闪频数呈正相关变化,可有效指示关中地闪发展趋势。雪粒子落区相对连续、在地闪周围,霰粒子相对分散、中心靠近地闪密集区。雷暴成熟阶段,雪、霰粒子分别在8~16km、6~12 km高度附近,密集区与显著上升运动区一致。上升运动偏强时,地闪平均电流和雨强偏大,与雪粒子空间相关性明显;上升运动偏弱时,地闪平均电流和雨强偏小,与霰粒子相关性明显。地闪频次峰值出现在对流云发展最高时段,频次成倍增�
Spatial and temporal distribution of cloud-to-ground （CG） flashes and mesoscale characteristics of two heavy wet thunderstorm processes with most CG lightning in the last 10 years at Guanzhong, which occurred re- spectively on August 11 12, 2010 （the ＂0811＂） and August 15 -- 16, 2011 （the ＂0815＂ ）, were analyzed by using NCEP reanalysis, CG lightning, satellite, Radar and WRF data. The results show that heavy wet thunder- storms at Guanzhong occurred favorably under the circulation background of two-through and one-ridge in Eura- sia mid-high latitude, and Shaanxi province is controlled by the stable West Pacific Subtropical High. Low level shear line is the ~irectly influence system. During thunderstorm, cold advection on upper levels and moist baro- tropic potential vorticity move southward, the energy frontal zone over northern Shaanxi move southward and in- vade the unstable stratification environment over central and southern Shaanxi. The low-level warm tongue over southwest of Shaanxi extend to the northeast. With unstable stratification increasing and high humidity at the early stage, the unstable energy at Guanzhong increases significantly with CAPE （ Convective Available Potential Ener- gy） above 3 000 J·kg-1. The vertical ascending motion is strong and deep. Aforementioned characteristics pro- vide favorable environmental conditions for strong wet thunderstorm. The West Pacific Subtropical High develops strongly and westward, unstable stratification with dry air at high levels and wet at low levels, high temperature and humidity near surface layer, obviously CAPE, relatively high altitudes of vertical motion center and convec- tive cloud, above factors are important reasons for that heavy wet thunderstorms have more CG flashes than ordi- nary rainstorms. The accumulated areas of CG flashes are consistent with the high potential temperature areas at lower levels, which also mainly located near positive helicity that below 50 m-2s-2. There is a significant difference between the d
出处
《高原气象》
CSCD
北大核心
2018年第1期167-184,共18页
Plateau Meteorology
基金
高原与盆地暴雨旱涝灾害四川省重点实验室科技发展基金项目(SZKT2017002)
陕西省气象局青年基金项目(2017Y-25)
中国气象局预报员专项(CMAYBY2017-074)
关键词
雷暴
地闪
环境条件
冰相粒子
WRF模式
Thunderstorm
Cloud-to-Ground lightning
environment conditions
ice phase particles
WRF model
