Estimation of Wind Direction in Tropical Cyclones Using C-Band Dual-Polarization Synthetic Aperture Radar
|Author(s)||Fan Shengren1, Zhang Biao1, 2, Mouche Alexis3, Perrie William4, Zhang Jun A.5, Zhang Guosheng1, 2|
|Affiliation(s)||1 : Nanjing Univ Informat Sci & Technol, Sch Marine Sci, Nanjing 210044, Peoples R China.
2 : Southern Marine Sci & Engn Guangdong Lab, Zhuhai 519082, Peoples R China.
3 : Inst Francais Rech Exploitat Mer, Lab Oceanog Phys Spatiale, F-29280 Plouzane, France.
4 : Fisheries & Oceans Canada, Bedford Inst Oceanog, Dartmouth, NS B2Y 4A2, Canada.
5 : Univ Miami, Hurricane Res Div, NOAA, Atlantic Oceanog & Meteorol Lab,Cooperat Inst Mar, Miami, FL 33149 USA.
|Source||Ieee Transactions On Geoscience And Remote Sensing (0196-2892) (Ieee-inst Electrical Electronics Engineers Inc), 2020-02 , Vol. 58 , N. 2 , P. 1450-1462|
|WOS© Times Cited||5|
|Keyword(s)||Synthetic aperture radar, Radar polarimetry, Wind speed, Atmospheric modeling, Spaceborne radar, Radar measurements, Synthetic aperture radar (SAR), tropical cyclone (TC), wind direction|
Under extreme weather conditions, the imprints of kilometer-scale marine atmospheric boundary layer roll vortices on the ocean surface are clearly visible in synthetic aperture radar (SAR) images of storms. Therefore, information about wind direction in storms can be obtained by analyzing SAR image features caused by boundary layer rolls. VH-polarized SAR imagery captures the structural features of storms well and shows prominent image gradients along the radial directions of the storm. The signal-to-noise ratios of VH-polarized images are small in low wind speed areas, but they are large in the same regions of VV-polarized images. Also, the capability of retrieving the atmospheric rolls orientation in VV-polarization is found to be sensitive to incidence angle, with better performances for larger incidence angles. Thus, there is the potential to retrieve the storm's wind directions using a combination of the VH- and VV-polarized SAR observations. In this article, we use the local gradient method to estimate tropical cyclone (TC) wind directions from C-band RADARSAT-2 and Sentinel-1A dual-polarization (VV & x002B; VH) SAR imagery. As a case study, wind directions with a spatial resolution of 25 km are derived by using both wide-swath VV- and VH-polarized SAR imagery over two hurricanes (Earl and Bertha) and one Typhoon (Meranti). We compare wind directions derived from ten dual-polarization SAR images with collocated wind directions from buoys, Global Positioning System (GPS) dropsondes, scatterometer, and radiometer. Statistical comparisons show that the wind direction bias and root-mean-square error are, respectively, -0.54 & x00B0; and 14.78 & x00B0; for VV-polarization, 0.38 & x00B0; and 14.25 & x00B0; for VH-polarization, 0.20 & x00B0; and 13.30 & x00B0; for VV- and VH-polarization, suggesting dual-polarization SAR is more suitable for the estimation of TC wind directions than VV- or VH-polarization SAR.