一次低纬高原暖区暴雨对流系统演变及边界层触发

Convective Systems Evolution and Boundary Layer Trigger During a Warm Sector Rainstorm over Low Latitude Plateau

利用高空和地面区域站、FY2G卫星TBB、昆明C波段多普勒雷达、闪电观测资料和NCEP/NCAR1°×1°再分析资料,分析了2017年7月12-13日云南副高外围暖区暴雨对流系统演变特征及边界层触发成因。结果表明,滇东中部和滇中中部暴雨,12日08:00以锋面降水为主,14:00后以暖区降水为主;环境场具有弱垂直风切变,湿层深厚,暖云厚度大,抬升凝结高度低等特征,利于降水持续及强降水触发,但昆明对流有效位能111.6~217.3 J/kg,暴雨对流性较弱;降水具有低质心对流结构,属于暖云性质,降水粒子以液态为主,伴有稀疏负闪;暴雨中心降水有3次波动,其中白邑初始对流的产生,是由于其西北侧山脉附近对流降水形成冷池,山脚地形性辐合线加强南移,此后在深厚偏南气流引导下,不断有25~30 dbz回波以1~5.1 m/s的速度经过白邑,形成列车效应,加之冷池作用下,地面辐合线再次加强影响白邑,形成午后降水峰值,夜间降水峰值的形成仅与偏南气流脉动有关,而格里三次降水波动,均是偏南气流脉动下形成列车效应,加之地面伴有中尺度气旋活动。

Based on upper air and surface regional automatic station observational data,the blackbody temperature of FY2G satellite infrared images,C wave band Doppler radar in Kunming and lightning sounding data,NCEP/NCAR 1°×1°reanalysis data,the evolution characteristics of convective systems and trigger causes of boundary layer during a Yunnan warm sector rainstorm at the edge of subtropical high pressure that occurred in 12 to 13 July 2017 are analyzed.The results showed that the rainstorm in the central eastern and central Yunnan is main front precipitation at 08:00 BT 12 and warm sector precipitation after 14:00 BT.Environment field has these characteristics,such as weak vertical wind shear,deep wet layer,large thickness of warm cloud,low lifting condensation level,which favoured the duration and maintenance of precipitation.However,convective available potential energy over Kunming is from 111.6 to 217.3 J/kg,convection of this warm sector rainstorm is weak.Precipitation has low centroid convective structure,belonged to warm cloud property.The phase state of precipitation particles in cloud cluster was main liquid and accompanied with sparse negative lightning.Centers of rainstorm had 3 times fluctuation,among them,the generation of initial convections in Baiyi is due to convective precipitation forming cold pool nearby mountains on the northwest side of Baiyi,topography convergence line along foothill belt strengthened and effected Baiyi.Thereafter,with the guide of deep south airflow,there is 25-30 dbz echoes by 1-5.1 m/s velocity continuously passing by Baiyi,formed train effect,together with the role of cold pool,surface convergence line strengthened and effected Baiyi once again,which formed precipitation peak in the afternoon.The formation of precipitation peak at night only related to pulsation of south airflow.Cubic fluctuation of precipitation in Geli related to pulsation of south airflow forming train effect,together with activity of mesoscale cyclone on the surface.