Abstract
The spaceborne synthetic aperture radar (SAR) cross-polarization signal remains sensitive to sea surface wind speed with high signal-to-noise ratio under tropical cyclone (TC) conditions. It has the capability of observing TC intensity and size information over the ocean with large coverage and high spatial resolution. In this paper, TC wind distribution characteristics were studied based on SAR images. We collected 41 Sentinel-1A/B cross-polarization images covering TC eye, which were acquired between 2016 and 2020. For each case, sea surface wind speeds were retrieved by the modified MS1A model in a spatial resolution of 1 km. After deriving the value and location of maximum wind speed, wind fields were simulated symmetrically within a 200 km radius. Two new methodologies were proposed to calculate the decay index and the symmetry index based on the retrieved and simulated wind fields. Characteristics of the two indices were analyzed with respect to maximum wind. In addition, the maximum and averaged wind speeds of the right, back and left side of the motion direction were compared with TC intensity and storm motion speed. Statistical results indicate that right-side wind speed is the strongest for maximum and average, the wind difference between the left and right side is dependent on storm motion speed.
Highlights
As one of the most destructive natural disasters on earth, tropical cyclones (TC) cause tremendous loss of life and property every year [1,2]
We investigated the relationships of all retrieved or calculated parameters: Um, rm, Corwr, decay index (DI), symmetry index (SI), and storm motion speed
Surface wind speed is an important factor in TCs
Summary
As one of the most destructive natural disasters on earth, tropical cyclones (TC) cause tremendous loss of life and property every year [1,2]. Several variables, such as heat, moisture, and momentum fluxes between air and sea, are closely related to the sea surface wind field [3,4,5]. Decay and asymmetry are two key features used to describe storm structures, which are impacted by intensity, storm motion speed and wind shear [9]. TCs have an asymmetric wind field, indicating that the radial wind distribution varies with azimuth direction. The decay value is dependent on TC intensity according to National Oceanic and Atmospheric Administration (NOAA)
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