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Wind/rain backscatter modeling and wind/rain retrieval for scatterometer and synthetic aperture radar.

机译：风/雨反向散射建模和风/雨回波，用于散射仪和合成孔径雷达。

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摘要

Using co-located space-borne satellite (TRMM PR, ESCAT on ERS 1/2) measurements, and numerical predicted wind fields (ECMWF), the sensitivity of C-band backscatter measurement to rain is evaluated. It is demonstrated that C-band radar backscatter can be significantly altered by rain surface perturbation, an effect that has been previously neglected. A low-order wind/rain backscatter model is developed that has inputs of surface rain rate, incidence angle, wind speed, wind direction, and azimuth angle. The wind/rain backscatter model is accurate enough for describing the total backscatter in raining areas with relatively low variance. Rain has a more significant impact on measurements at high incidence angles than at low incidence angles. Using three distinct regimes, the conditions for which wind, rain, and both wind and rain can be retrieved from scatterometer backscatter measurements are determined.;The effects of rain on ESCAT wind-only retrieval are evaluated. The additional scattering from rain causes estimated wind speeds to be biased high and estimated wind directions to be biased toward the along-track direction in heavy rains. To compensate for rain-induced backscatter, we develop a simultaneous wind/rain retrieval method (SWRR), which simultaneously estimates wind and rain from ESCAT backscatter measurements with an incidence angle of over 40 degrees. The performance of SWRR under typical wind/rain conditions is evaluated through simulation and validation with collocated TRMM PR and ECMWF data sets. SWRR is shows to significantly improve wind velocity estimates and the SWRR-estimated rain rate has relatively high accuracy in moderate to heavy rain cases.;RADARSAT-1 ScanSAR SWA images of Hurricane Katrina are used to retrieve surface wind vectors over the ocean. Collocated H*wind wind directions are used as the wind direction estimate and the wind speed is derived from SAR sigma° by inversion of a C-band HH-polarization Geophysical Model Function (GMF) that is derived from the VV-polarization GMF, CMOD5, using a polarization ratio model. Because existing polarization models do not fit the ScanSAR SWA data well, a recalibration model is proposed to "recalibrate" the ScanSAR SWA images. Validated with collocated H*wind wind speed estimates, the mean difference between SAR-retrieved and H*wind speed is small and the root mean square (RMS) error is below 4 m/s. Rain effects on the ScanSAR measurements are analyzed for three different incidence angle ranges using collocated ground-based Doppler weather radar (NEXRAD) rain measurements. Compared with the scatterometer-derived model, the rain-induced backscatter observed by the ScanSAR at incidence angles 44°--45.7° is consistent with the scatterometer-derived model when the polarization difference between HH and VV polarizations is considered.
机译：使用位于同一地点的星载卫星（TRMM PR，在ERS 1/2上为ESCAT）的测量结果和数值预测的风场（ECMWF），评估了C波段反向散射测量对降雨的敏感性。事实证明，雨带表面扰动可以显着改变C波段雷达的反向散射，而这种影响此前已被忽略。建立了一个低阶风/雨反向散射模型，该模型具有地表降雨率，入射角，风速，风向和方位角的输入。风/雨后向散射模型足够准确，可以描述方差相对较低的下雨地区的总后向散射。高入射角下的雨水比低入射角下的雨水对测量的影响更大。使用三种不同的模式，确定了可以从散射仪反向散射测量值中获取风，雨以及风和雨的条件。;评估了雨水对ESCAT纯风获取的影响。在大雨中，来自雨水的额外散射导致估计的风速偏高，导致估计的风向偏向沿航迹方向。为了补偿雨水引起的反向散射，我们开发了一种同时进行风/雨的反演方法（SWRR），该方法可以根据入射角超过40度的ESCAT反向散射测量值同时估算风和雨。通过并置的TRMM PR和ECMWF数据集进行仿真和验证，可以评估SWRR在典型风/雨条件下的性能。结果表明，SWRR可以显着改善风速估计，并且在中度到重度降雨的情况下，SWRR估计的降雨率具有相对较高的准确性。；飓风卡特里娜的RADARSAT-1 ScanSAR SWA图像用于检索海洋上的地面风向矢量。将并置的H *风向用作风向估计值，并通过对C波段HH极化地球物理模型函数（GMF）进行反演，从SAR sigma°得出风速，该函数从VV极化GMF，CMOD5 ，使用极化率模型。由于现有的偏振模型无法很好地拟合ScanSAR SWA数据，因此提出了一种重新校准模型来“重新校准” ScanSAR SWA图像。通过并置的H *风速估计值进行验证，SAR检索的风速与H *风速之间的平均差很小，并且均方根（RMS）误差低于4 m / s。使用并置的地面多普勒天气雷达（NEXRAD）降雨测量，分析了三个不同入射角范围内降雨对ScanSAR测量的影响。与散射计派生的模型相比，在考虑HH和VV极化之间的极化差异时，ScanSAR在入射角为44°--45.7°时观察到的雨致反向散射与散射计派生的模型一致。

著录项

  • 作者

    Nie, Congling.;

  • 作者单位

    Brigham Young University.;

  • 授予单位 Brigham Young University.;
  • 学科 Engineering Electronics and Electrical.;Engineering Marine and Ocean.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 129 p.
  • 总页数 129
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 无线电电子学、电信技术;海洋工程;
  • 关键词

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