回波强度垂直廓线与雷达定量估测降水的关系

Relations Between Vertical Profile of Reflectivity and Radar Quantitative Precipitation Estimation

为了分析不同高度回波强度与地面降水的关系,提高雷达定量估测降水的能力,本文对石家庄2006~2008年5~9月共77次降水过程的反射率因子垂直廓线（VPR）进行了统计分析。对比降水实况和VPR发现,各个高度层的反射率因子波峰（谷）同降水波峰（谷）相一致,而且降水强度越大,反射率因子核心高度越低。同时,还比较了距离雷达站不同的水平距离和不同海拔高度的反射率因子特征,发现海拔高度对5 mm/h以下降水率和垂直高度在4 km以下各层的反射率因子会造成一定的影响,而对强降水和高层反射率因子影响较小。另外,零度层亮带在VPR上表现出反射率因子增大的特征,影响降水估测效果。为了消除零度层亮带的影响,选取1.5~3.5 km为估测降水的最佳高度范围,各站具体选取高度则取决于其距雷达站的水平距离和海拔高度。

In order to improve the ability of radar quantitative precipitation estimation（ QPE）,the relations between ground rainfall and echo reflectivity at different heights were analyzed based on 77 vertical profiles of reflectivity（ VPR） during the rainfall processes in summer（ May to September） from 2006 to 2008 in Shijiazhuang. By comparison actual rainfall and VPR,the wave peaks /valleys of reflectivity in each level were consistent with more /less rainfall,and the larger the rainfall intensity,the lower the height of reflectivity core. Furthermore,the characters of reflectivity in different distance from radar station and different altitude were contrasted,in some extent,the altitude can influence the rainfall rate when it was less than 5 mm /h and the reflectivity factor when the vertical height was below 4 km,but little effect on the severe precipitation and the reflectivity factors in higher layers. The precision of QPE was influenced by zero-layer bright band because its reflectivity factor enhancing in VPR,in order to avoid the influence of zero-layer bright band,the optimum height from 1. 5 to 3. 5 km was selected for QPE. The particular height selected in different station depends on the horizontal distance from radar and altitude of stations.