2019年夏季三江源局地热对流云宏微观特征的初步分析

Preliminary Analysis on Thermal Convective Clouds Generated Locally in Summer of 2019 in Sanjiangyuan Region

在中国气象局西北人影工程项目的支持下,2019年8—9月在青海省三江源地区增设714XDP车载X波段双偏振多普勒雷达开展局地热对流云观测试验。主要基于雷达体扫观测数据分析研究某日高原局地热对流云的宏微观特征,同时将FY-4A卫星反演对流云特征与雷达观测热对流云回波进行点对点对比。结果表明:该日试验区具备局地热对流云形成的动力条件、热力条件和一定的水汽条件;回波自西北向东南移动,与地形的走向呈90°或150°夹角(顺时针方向),与500 hPa流场方向一致,多数移速大于35 km/h;高原局地热对流云宏观特征表现为最大回波强度较小(30~48 dBz),最大回波顶高4~5 km,冷云过程为主,垂直积分液水含量较小(<1 kg/m^(2)),持续时间较短(30~90 min);分析典型个例认为动力抬升对高原局地热对流云发展起主要作用,其发展成熟阶段零度层以上粒子相态以冰晶、过冷水、霰或小雹为主;对比FY-4A卫星反演对流云特征与热对流云回波的异同,云粒子有效半径较大(>16μm)的像素点与回波强度大值对应较好。

With the support of Northwest weather modification project,CMA,observational experiments of local thermal convective clouds were conducted in Sanjiangyuan Region in August and September 2019.Based on on-board X-band dual polarization doppler radar volume-scan data,this paper mainly makes analysis of macroscopic and microscopic characteristics of thermal convective clouds occurred on one day,and makes comparison in point-to-point between satellite observation and radar echoes of thermal convective clouds.The results show that:experimental area had requirements for formation of local thermal convective clouds;movement of thermal convective clouds was from northwest to southeast,whose direction formed a 90°or 150°with topography(clockwise direction)and accorded with wind fields of 500 hPa,and most speed of movement was more than 35 km/h;radar echoes of thermal convective clouds were weak(with 30 to 48 dBz of maximal radar echo reflectivity),which maximal echo top varied from 4 to 5 km;thermal convective clouds were formed by cold cloud mechanism,with less vertical integrated liquid water contents and shorter duration;thermal convective cloud within a typical example was mainly affected by dynamic lifting,and its types of hydrometeor higher than 0°layer consisted of ice crystal,supercooled liquid water and graupel or small hail in developing and mature stages;comparing retrieval Re from FY-4A satellite observation with radar echoes of thermal convective clouds,the two were in good consistency.