甘肃一次冰雹过程降水及闪电活动特征

Characteristic of Precipitation and Lightning Activity of a Hailstorm Event in Gansu Province

利用热带测雨卫星(TRMM)的测雨雷达(PR)、微波辐射计(TMI)和闪电成像仪(LIS)资料分析2012年8月25日甘肃省一次较强冰雹过程。结果表明,本次过程受3个分散的β中尺度对流系统影响,对流云像素点约为层云的1/2,对流云平均降水率是层云的8.2倍。冰雹云回波顶高度近13 km,回波强度大于55 dBZ的最大高度为7.5 km左右,降水率大于45 mm·h^-1的云层厚度约7 km。降水廓线反映出降水率垂直分布不均匀,对流降水中50、10 mm·h^-1的降水率随着高度的升高先增加后减小,在9 km左右减小明显。此次冰雹过程的闪电发生临近处6 km雷达反射率高于40 dBZ,85 GHz极化修正亮温低于210 K。

The characteristics of precipitation and lightning activity of a strong hailstorm occurring in Gansu Province on 25 August 2012 were studied by using the data from precipitation radar(PR), microwave imager(TMI) and lightning imager sensor(LIS) boarded on the TRMM(tropical rainfall measuring mission) satellite. The results show that there were three dispersed meso-β scale convective systems by analyzing the horizontal structure of the hailstorm. Although the pixel points of convection precipitation were less than that of stratiform precipitation, the averaged rain rate of convective precipitation was 8.2 times larger than that of stratiform precipitation. The top of the hail cloud could reach up to 13 km above ground with strong echoes(>55 dBZ) below about 7.5 km. The cloud thickness with the precipitation rate greater than 45 mm·h^-1 was 7 km. The vertical distribution of precipitation profiles under different rain rates showed inhomogeneous characteristic. The precipitation rates of 50 mm·h-1 and 10 mm·h^-1 increased first at lower levels and then decreased with the increase of height,their initial reduced height was about 9 km. Analysis of lightning activity of the hail precipitation process showed that most lightning flashes occurred near the strong convective region with radar echoes higher than 40 dBZ and polarization corrected brightness temperature of 85 GHz channel was lower than 210 K.