热带测雨卫星的星载雷达和地基雷达探测云回波强度及结构误差的模拟分析

为了揭示热带测雨卫星上的测雨雷达热带测雨卫星的星载雷达与X波段多普勒雷达在探测云的反射率因子的大小和结构方面的差异 ,用散射模式和数值模拟的方法讨论了这两种雷达的波长、雷达波入射方向、波瓣宽度等参量对反射率因子的大小和结构的影响 ,并利用所得结果讨论了两种雷达实际观测的差异。结果表明 :雷达波长和入射方向的不同引起的两种雷达测量的反射率因子的差异在 2 .0dBz以内 ,TRMMPR可在强回波中心探测到更大的反射率因子 ,并在很大程度上平滑了回波的结构 ,在强回波和弱回波区分别低估和高估 3～ 5dBz,造成了观测的云的面积增大、平均回波强度减小、面积积分降水量增大。这些理论结果还不能完全揭示两种雷达实际观测结果的差异 ,看来星载雷达和地基雷达探测结果的对比问题很复杂 ,其中雷达波的衰减问题是必须考虑的。

SIMULATION AND ANALYSIS ON OBSERVATION ERRORS OF CLOUD INTENSITY AND STRUCTURE WITH TRMM PR AND GROUND-BASED RADAR

In order to explain theoretically the difference of observed cloud intensities and structures by TRMM PR and ground-based radar, the effects of wavelengths, orientations of radar waves and radar beam width on the observations of reflectivity were simulated. The results show that the error due to the different wavelength and orientation of radar wave is within 2.0 dBz, TRMM PR can observe larger reflectivity than ground-based radar in echo center. TRMM PR smoothes the cloud structure, overestimates and underestimates 3-5 dBz in strong and week echo areas, respectively. Beam width and long distance from TRMM PR to target cause TRMM PR to observe large echo area and area integrated rainfall amount and weak averaged echo intensity. The theoretical results above can only explain part of observed facts, which means that the comparison of observation result between TRMM PR and ground-based radar is complicated, the attenuation of radar wave within precipitation area is the main factor to affect the observed result.