Vertical Air Motions and Raindrop Size Distributions Estimated Using Mean Doppler Velocity Difference From 3- and 35-GHz Vertically Pointing Radars
Vertical Air Motions and Raindrop Size Distributions Estimated Using Mean Doppler Velocity Difference From 3- and 35-GHz Vertically Pointing Radars
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使用 3GHz 和 35GHz 垂直指向雷达的平均多普勒速度差估算垂直空气运动和雨滴尺寸分布
DOI：
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发表时间：
2016
影响因子：
8.2
通讯作者：
V. Chandrasekar
中科院分区：
文献类型：
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作者：
C. Williams;R. Beauchamp;V. Chandrasekar
利用两台工作在3GHz和35 GHz的并置垂直指向雷达（VPRs），对层状雨中的垂直空气运动和雨滴尺寸分布（DSD）的垂直廓线进行了估计。不同的雨滴后向散射截面发生在3和35 GHz的瑞利散射发生在3 GHz的所有雨滴和米氏散射发生较大的雨滴在35 GHz。这种依赖于频率的后向散射截面导致不同形状的反射率加权多普勒速度谱，从而导致雷达发射频率依赖的固有反射率因子、平均多普勒速度和谱方差的雷达矩。本文描述的检索方法使用四个雷达矩作为输入，以检索降水柱内每个高度处的四个输出。输入包括3GHz VPR平均多普勒速度和未衰减反射率因子以及35 GHz VPR平均多普勒速度和频谱方差。输出包括垂直空气运动和三个参数的伽玛形DSD。考虑到不同的VPR样本量，雷达观测积累超过45秒，并在几个范围门代表时间-空间尺度大于任何VPR样本量。在这个共同的时空尺度上观察到的变化被用来估计检索的不确定性。检索的空气运动和DSD参数比较以及检索从并置的449 MHz VPR，估计空气运动从布拉格散射信号和DSD参数从瑞利散射信号。
Vertical profiles of vertical air motion and raindrop size distributions (DSDs) within stratiform rain are estimated using two collocated vertically pointing radars (VPRs) operating at 3 and 35 GHz. Different raindrop backscattering cross sections occur at 3 and 35 GHz with Rayleigh scattering occurring for all raindrops at 3 GHz and Mie scattering occurring for larger raindrops at 35 GHz. This frequency-dependent backscattering cross section causes differently shaped reflectivity-weighted Doppler velocity spectra leading to radar transmit frequency-dependent radar moments of intrinsic reflectivity factor, mean Doppler velocity, and spectrum variance. The retrieval method described herein uses four radar moments as inputs to retrieve four outputs at each height within a precipitation column. The inputs include 3-GHz VPR mean Doppler velocity and unattenuated reflectivity factor and 35-GHz VPR mean Doppler velocity and spectrum variance. The outputs include vertical air motion and three parameters of a gamma-shaped DSD. To account for different VPR sample volumes, radar observations were accumulated over 45 s and over several range gates to represent time-space scales larger than either VPR sample volumes. Observed variability over this common time-space scale is used to estimate retrieval uncertainties. The retrieved air motions and DSD parameters compare well against retrievals from a collocated 449-MHz VPR that estimated air motions from Bragg scattering signals and DSD parameters from Rayleigh scattering signals.