区域雷达网同步观测对比分析  

A CONTRAST ANALYSIS OF SYNCHRONOUS OBSERVATIONS FROM REGIONAL RADAR NETWORK

作　　者：肖艳姣[1] 刘黎平[2] 杨洪平[1] 

机构地区：[1]中国气象局武汉暴雨研究所,武汉430074 [2]中国气象科学研究院灾害天气国家重点实验室,北京100081

出　　处：《气象学报》2007年第6期919-927,共9页Acta Meteorologica Sinica

基　　金：武汉区域气象中心科技发展基金课题(QY-Z-200706);国家重大基础研究项目(2004CB418305);武汉暴雨研究所基本科研业务费专项(0602)

摘　　要：利用长江中游的合肥、宜昌、武汉、常德和长沙雷达周围的1:25万的地形高度数据得到各雷达的混合扫描仰角和等射束高度拼图。选用2004年7月17—19日5部雷达同步观测的雷达体扫资料,分析了各雷达的最低扫描仰角;在尽量排除地物杂波、波束阻挡、距离衰减和波束展宽等因素影响的情况下,对比分析了5部雷达构成的有重叠覆盖区的7个雷达对的反射率因子差异。结果表明:(1)对雷达最低扫描仰角进行分析可以检查雷达的仰角标定,武汉和合肥雷达平均最低观测仰角比VCP21扫描方式规定的要低;(2)用雷达对等距离线上的反射率垂直剖面可以分析雷达对同步观测的回波空间位置和强度差异,常德雷达和其周围雷达同步观测的回波高度明显偏低;(3)用雷达对等距离线上某高度的反射率因子曲线变化的一致程度可以分析雷达的方位标定,这5部雷达没有明显的方位定标偏差;(4)用雷达对等距离线上某高度的平均反射率因子差可以分析雷达对同步观测的系统观测差,宜昌雷达和其周围的雷达相比,观测的回波强度偏强,而武汉和其周围的雷达相比,观测的回波强度偏弱;(5)反射率因子差的时间平均值随着反射率因子的大小变化而变化,当观测的反射率因子越大时雷达对的反射率因子差的时间平均值也越大。On the basis of the 1：250000 DEM（digital elevation model） data and station information of Hefei, Wuhan, Yichang, Changde and Changsha weather radars and radar beam pattern （or power density function）, the beam blockage coefficients is calculated. A beam bottom clearance of 150 m or more and an occultation of less than 60 % are used to define a hybrid elevation angle which is used for calculating iso-beam height based on radar altimetry. After iso-beam heights from individual radars are remapped onto the Cartesian grid, they are combined to produce a mosaic iso-beam height image. 7 radar pairs are composed, which have common covering area at 4 km height. The lowest scanning elevation angles of the 5 radars are analyzed using the radar raw data on 17 - 19, July 2004, the results show that the mean lowest elevation angles of Hefei and Wuhan radars are respectively 0.19°and 0.07° lower than 0.5°, the regulation of VCP21, and the others have no great difference. And then, after distance attenuation, and terrain obstruct and clutter are eliminated, the reflectivity difference of radar pair on the equidistant line are analyzed when they simultaneously observe. Because of different height above sea level of radar antenna, the objects＇ height at the same slant range with same elevation angle are dissimilar between radar pairs. In order that two contrast reflectivities come from same object more possible, the radar volume scan data are remapped onto 3D Cartesian grid, and for abating the attenuation influence, the reflectivities on equidistant line are selected, and for mitigating beam blockage and clutter, when the mean reflectivity difference between radar pair at same distance from two radars are calculated, only these points are considered whose height is higher than iso-beam height, viz. which are not blocked completely. Whereby, the following results can be approached： （1） Lowest scanning elevation angles can be used to examine the calibration of radar elevation angle. （2） Vertical cross sect

关 键 词：区域雷达网 同步观测 反射率因子差 对比分析 

分 类 号：TN957.52[电子电信—信号与信息处理] TP873[电子电信—信息与通信工程]