青藏高原地区TRMM PR地面降雨率的修正

Correction of TRMM PR Surface Rainfall Rates over the Tibetan Plateau

为掌握并改进青藏高原地区TRMM卫星降水雷达(precipitation radar,PR)地面降雨率准确度,统计分析了2005—2007年TRMM PR 2A25资料和逐小时地面雨量计,结果表明:青藏高原地区TRMM PR地面降雨率在层云降水时平均偏低35%,在对流云降水时平均偏高42%。Z-R关系的适用性是PR产生偏差的原因之一,研究将TRMM PR层云降水模型中20℃层Z-R关系的初始系数A和b分别修正为0.0288和0.6752,对流云降水模型中20℃层的初始系数A和b分别修正为0.0406和0.5809,得到两类降水模型0℃层与20℃层之间不同高度Z-R关系的更新系数。检验结果表明,修正降水模型后能够提高青藏高原地面降雨率测量的准确度。

In order to reveal and improve the accuracy of surface rainfall rates derived from precipitation radar(PR) on TRMM satellite over the Tibetan Plateau,TRMM PR 2A25 products and hourly rain gauge data from 2005 to 2007 are compared.Results show that PR has a relative error of —35%in stratiform rain and42%in convective rain over the Tibetan Plateau.The applicability of Z-R relation is one of the cause for the bias of PR.Based on the analysis,the initial coefficients A and b in Z-R relations at 20℃ level are modified to 0.0288 and 0.6752 for stratiform rain,respectively,also modified to 0.0406 and 0.5809 for convective rain,thus the Z-R relation at different altitudes between 0 ℃ and 20 ℃ height are updated.Results suggest that the modified models can achieve better accuracy in estimating surface rainfall rates over the Tibetan Plateau.