X波段双线极化雷达差分反射率的衰减订正  

Attenuation Correction of Radar Differential Reflectivity for X-Band Dual Polarization Radar

作　　者：何宇翔[1,2] 吕达仁[1] 肖辉[1] 

机构地区：[1]中国科学院大气物理研究所,北京100029 [2]中国科学院研究生院,北京100049

出　　处：《高原气象》2009年第3期607-616,共10页Plateau Meteorology

基　　金：国家自然科学基金面上项目(40875080);国家科技支撑计划项目(2006BAC12B00-1);中国科学院知识创新工程青年人才领域前沿项目(IAP07408);中国气象局与吉林省人民政府人工影响天气联合开放实验室开放课题(0603)共同资助

摘　　要：同时发射水平和垂直极化电磁波的双线极化雷达,能同时获取两个通道的反射率和相位。使用极化雷达极化分集的物理基础是降水粒子在下落过程中总是呈现扁椭球形状,在平衡时,降水粒子椭率与其体积有关,差分反射率就是衡量粒子椭率大小的物理量。但是由于水平和垂直方向的差异,导致了这两个方向的衰减出现差异,进而导致差分反射率不能真实地反映粒子的椭率大小,所以必须进行衰减订正。本文使用实际雷达回波资料,利用反射率和差分反射率之间的约束关系,同时考虑了探测仰角对差分反射率的影响,通过统计拟合的方法,确定了差分衰减与差分传播相移之间的关系。在此基础上,比较了一次层状云个例的两个比较均匀降水区域在订正前后的差异。结果表明,雷达RHI、PPI图像在订正前后发生了明显的变化,差分反射率与反射率之间的关系得到改善,说明这种订正方法的可行性和实用性。这种使用实际雷达资料本身的约束关系进行订正的方法,可以灵活地根据不同的雷达、不同的地点、不同的天气环境统计相应的订正参数,因此避免了诸如温度等的变化对订正参数的影响,具有较好的实际应用前景。Two channels reflectivity and phase can be acquired by dual polarization radar which can transmit horizontal and vertical polarized electromagnetic waves simultaneously. The physical basis of using polarization radar is that the precipitation particles always exhibit oblate ellipse shape during falling. The ratio of major and minor axis of precipitation particle is related with the volume at balance. Differential reflectivity is the measurement of physical essence of ellipticity of the particle. Unfortunately, differences between horizontal and vertical lead to attenuation difference along the two directions, resulting in the attenuated differential reflectivity can not reflect particle ellipticity any more, so it is absolutely necessary to do attenuation correction. On the basis of actual radar reflectivity data, the paper uses the relation- ship between reflectivity and differential reflectivity, by statistical fitting method and taking into account the detecting elevation angle effects on differential reflectivity, the relationship between differential attenuation and propagation phase is determined. Thus the difference between before and after correction of two relatively homogeneous rain areas in stratiform precipitation is compared. Results show that Radar RHI and PPI images are significantly changed after correction, and the relationship between corrected differential reflectivity and reflectivity is improved, which indicates the feasibility and practicability of this method. The method can statistically determine correction parameters, and can be used flexibly according to different radar, location and weather, since it is based on the constraint relationship of its own actual radar data, thus it can avoid that changing quantities such as temperature exert an influence on correction parameters.

关 键 词：双线极化雷达 差分反射率 衰减订正 

分 类 号：P412.25[天文地球—大气科学及气象学]