星载测雨雷达探测频段选择仿真研究

A simulation research on the wave bands selection of a satellite-borne rain measuring radar

在星载测雨雷达必须满足的3个基本条件的基础上,开展了风云三号(FY-3)星载测雨雷达最佳波段组合的研究。文中将高精度GCE(Goddard cumulus ensemble)模式中BOB飓风资料的大气廓线和水凝物廓线作为三维Quickbeam气象雷达模拟软件的输入,分别模拟了5、10、14、35和94GHz 5个频点星载测雨雷达的探测性能。从近地面层获得较宽的降水动态范围的角度,雷达频点中必须要选择一个低频。在现有天线硬件条件以及科技水平的限制下,基本排除了5和10 GHz作为星载测雨雷达探测频点的可能性。14、35和94GHz 3个频点模拟探测台风不同区域时的等效雷达反射率因子和测量的雷达反射率因子的对比结果表明,雷达频点越高,受衰减的影响就越严重,因此94 GHz频点不适合作为星载测雨雷达的探测频点。考虑到高频点对弱降水探测的敏感性比较高,能够弥补低频点在弱降水区域受到敏感性限制的缺点。因此,高频点可以用来探测弱降水。最后,综合星载测雨雷达的频率配置分析结果,确定使用位于13.40—14.00GHz以及35.50—35.60GHz的Ku和Ka波段作为FY-3号星载测雨雷达的主探测波段。Ku波段有利于探测强降水,Ka波段则有利于探测弱降水,两者结合形成的双频探测有利于提高降水反演的精度。

Based on the three basic requirements which should be met by a satellite-borne rain-measuring radar,researches on the combination of the soundest wave bands for FY-3 a satellite-borne rain-measuring radar have be made.The profiles of hydrometers and gases output by the high-precision three-dimensional（3D）Goddard cumulus ensemble（GCE）model are used as the input of the Quickbeam radar simulation software.The detection nature for the five frequencies of 5,10,14,35 and 94 GHz is discussed.To obtain a sufficient dynamic range in the near surface layer,it is necessary to select a lower frequency.Under the restrictions of the existing antenna hardware and the current technology level,5 and 10 GHz are unpractical to be selected as the frequencies of the satellite-borne radar. The contrast analyses of the measured radar reflectivity factor and the effective reflectivity factor in three different typhoon areas show that there is an increasing attenuation with increasing high frequency.So,94 GHz can＇t be used to detect rain.However,a high frequency has a better sensitivity to light rain and can make up the sensitivity deficiency of low frequency;so,a high frequency can be employed to detect light rain.Finally,according to the frequency allocations determined by the International Frequency Registration Board,the Ka and Ku bands should be chosen and 13.40-14.00 GHz in the Ku band and 35.50-35.60 GHz in the Ka band should be the soundest wave bands combination.The Ku band is valid for detecting heavy rain while the Ka band is valid for detecting light rain.The bands of Ku and Ka can be connected to improve the precision of precipitation retrieval.