星载降水雷达机载校飞试验:地基多通道微波辐射计估算雷达路径积分衰减

Airborne experiment of spaceborne rain radar:Attenuation estimation of the Ka-band radar with ground-based multi-channel microwave radiometers

介绍了在雷达观测降水试验中如何配合利用地基微波辐射计估算雷达路径积分衰减(PIA)的一种方法。所用的GPS高空探空资料和地基多通道微波辐射计的观测资料,均为中国首次星载降水雷达机载校飞试验中获得的数据。由于常规探空资料中没有云水含量的直接信息,因此,通过绝热液态水含量分析方法,从GPS探空数据中计算得到这些云参数值。用MWMOD进行亮温模拟并计算液态水含量。在晴空条件下,用该模式模拟了地基多通道微波辐射计12个通道的下行辐射亮温。通过设置相对湿度阈值,利用MWMOD模式自带的绝热液态水含量分析方法,从探空廓线中分析出液态水廓线,进而模拟出有云情况下的下行辐射亮温。辐射传输模式的模拟亮温和地基多通道微波辐射计观测亮温的对比表明,进行云分析之后的模拟亮温值更接近于实测值。由此,利用由辐射传输模式和地基微波辐射计,从探空廓线中分析出液态水廓线,计算出有云情况下的大气整层透过率,进而得到路径积分衰减,为降水雷达衰减订正提供一种有效手段。

This paper focused on the research of attenuation correction method for weather radar observations.Based on the adiabatic liquid water content analyzing method and radiation transfer model（RTM）,the total attenuation of atmosphere was estimated by combining the GPS radiosonde atmosphere profile and the brightness temperatures observed by a ground-based multi-channel microwave radiometer.Under clear sky conditions,the brightness temperatures are simulated at 12 channels of the ground-based multi-channel microwave radiometer using MWMOD.It is found that when the relative humidity was set to a reasonable value,the liquid water profile can be estimated by using the adiabatic liquid water content analyzing method,while the difference between the model-simulated brightness temperature and the radiometer observation reached a reasonable value.Based on the estimated liquid water content,the path-integrated attenuation（PIA） of the ground-base radar can be computed.The results show that the PIA computation method suggested in this paper is an effective method to estimate the attenuation of ground-based weather radar echoes.