Spectral density of polarimetric variables separating biological scatterers in the VAD display
Spectral density of polarimetric variables separating biological scatterers in the VAD display
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DOI：
10.1175/jtech2043.1
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发表时间：
2007-07-01
影响因子：
2.2
通讯作者：
Zrnic, Dusan
中科院分区：
文献类型：
--
作者：
Bachmann, Svetlana;Zrnic, Dusan
本文介绍了用S波段双极化雷达观测到的两种生物散射体在大范围内混合的晴空回波。这起案件发生在2004年9月7日晚上，正值鸣禽（雀形目）秋季迁徙季节开始之际。偏振光谱分析用于区分鸟类和昆虫的多峰光谱。光谱峰的空间连续性表明昆虫（风）速度与鸟类速度有明显的分离。偏振变量的光谱密度表现出极大的不同的值在对应于昆虫的速度比从鸟类，允许分离的两种散射体类型。因此，从谱密度计算的固有极化变量的统计是无偏的，并且比用标准处理技术获得的统计更接近回波类型的集合统计。一种新的显示的频谱密度与方位角，称为频谱速度方位角显示（SVAD），构造更容易查看和解释的速度场。SVAD的分析揭示了两种类型的散射体的平均速度和方向。
Echoes in clear air from two types of biological scatterers mixed within the resolution volumes over a large region, observed with S-band dual polarization radar, are presented. This case occurred in the evening of 7 September 2004, at the beginning of the fall migrating season of song birds (passerines). Polarimetric spectral analyses are used for distinguishing birds and insects in multimodal spectra. Spatial continuity of spectral peaks shows clear separation of insect (wind) speeds from bird speeds. Spectral densities of polarimetric variables exhibit vastly different values at speeds corresponding to insects than from those of birds, allowing the separation of the two scatterer types. Therefore, the statistics of the intrinsic polarimetric variables computed from spectral densities are unbiased and closer to the ensemble statistics of the echo type than the ones obtained with standard processing techniques. A novel display of the spectral densities versus azimuth, termed spectral velocity-azimuth display (SVAD), is constructed for easier viewing and interpretation of the velocity field. Analyses of the SVADs reveal the mean velocities and the directions of the two types of scatterers.