多普勒雷达积分VAP反演技术  

AN INTEGRATIING VAP METHOD FOR SINGLE-DOPPLER RADAR WIND RETRIEVAL

作　　者：梁旭东[1] 王斌 

机构地区：[1]中国科学研究院大气物理研究所LASG

出　　处：《气象学报》2007年第2期261-271,共11页Acta Meteorologica Sinica

基　　金：国家自然基金课题(40405012);国家科技部科研院所社会公益研究专项(2005DIB3J104)

摘　　要：单多普勒雷达风场反演技术对于扩大多普勒雷达的应用范围具有重要的作用。在传统的反演技术中,VAD和VAP技术操作简单,原理清晰,具有一定的实用价值。本文在提出“按方位角均匀假定反演关系”的基础上,进一步证明VAD和VAP技术是“按方位角均匀假定反演关系”的两种特殊应用,进而把这两个方法统一起来。在此基础上,提出采用“按方位角均匀假定反演关系”进行二维风场反演的积分VAP技术(IVAP),该技术与传统VAP技术不同的是在整个选定的反演区间上进行二维风场反演,而不是仅考虑反演区间的两个端点,因此IVAP技术具有滤波性能,而且可以根据需要调整反演区间以得到满足一定平滑性并能反映中小尺度信息的风场信息。采用I-VAP技术反演时可以不对原始资料进行平滑预处理,因此使用中更为方便。当IVAP反演中积分区间为整个扫描圆周时,反演结果与VAD技术一致,而当反演时采用相邻的方位角时,反演结果与VAP技术一致。IVAP技术的频率响应函数表明:IVAP技术对于小尺度扰动具有滤波作用,而且当反演中采用的方位角区间越大时,对较短波动的滤除能力越强,得到的反演风场越平滑。理想试验采用均匀西风叠加小幅随机扰动的流场得到雷达观测径向风,对比分别使用VAP和IVAP方法,用不同的方位角区间反演的西风风速表明,IVAP方法能明显滤去随机高频扰动,而且反演采用的方位角区间越大,反演得到的西风越接近平均值。该试验表明,IVAP方法具有滤除小扰动的特性。采用IVAP方法对线性分布风场得到的雷达观测径向风反演表明,当反演采用的方位角区间较小时,反演结果能反映风场的线性分布特征,当反演的方位角区间逐渐增大时,反演结果越接近平均风场,即与VAD方法的反演结果越接近。该试验表明IVAP方法能得到较高分辨率的反演风场。Some widely-used methods have relative conceptual and practical simplicity. Among them, the simplest one is the VAD （velocity-azimuth display） technique which is based on the assumption that the horizontal wind field varies linearly in space. Another method is VAP （velocity-azimuth process） which assume that the horizontal wind vectors of two neighboring azimuths are uniform. The advantage of VAD is that it isn＇t affected by small perturbations of the radial wind along the azimuth, to which VAP method is very sensitive. Nevertheless, the VAD method has a very poor spatial resolution compared with the VAP method. However, as shown in this paper, the relationships used to retrieve the wind fields in the VAD and VAP methods are all special cases of the retrieval function based on the azimuthal uniform-wind assumption for a given azimuthal interval [ θ1, θ2 ]. When using this retrieval function to retrieve wind fields, the azimuthal interval used in retrieval can be varied according to the requirement of smoothness or resolution. The larger/smaller is the azimuthal interval, the coarser/finer the horizontal resolution of retrieved wind field, and the more insensitive/sensitive is the retrieval method to small scale perturbations. Because the whole information within the azimuthal interval [ θ1,θ2 ], instead of only the information at two terminal points, i.e. azimuths θ1, andθ2, are used to retrieve the wind fields, this method is referred to as the integrating VAP （IVAP） method, wherein horizontal wind field is retrieved using the Doppler velocity over the circular arc delimited by the given azimuthal interval times the scan radius. It is different from the VAP method wherein only the velocities at two terminal points of the given azimuthal interval are used. Therefore, the IVAP method has a filtering function, and the smoothness of the retrieved wind field can be obtained by adjusting the azimuthal interval. The filter which is required in the pre-process of VAP method is no longer necessary in

关 键 词：多普勒雷达 积分VAP 风场反演 

分 类 号：P415.2[天文地球—大气科学及气象学]