The Upwind/Downwind Dependence of the Doppler Spectra of Radar Sea Echo

摘要

The upwind/downwind dependence of the doppler spectra of radar sea echo was investigated using the coherent radar data collected with the Four-Frequency Radar (4FR) System at three frequencies: 428, 1228, and 4455 MHz. The data corresponded to sea conditions which varied from the relative calm found in Bermuda in January 1970, to 24-m/sec winds and 8-meter wave heights in the North Atlantic in February 1969. The bandwidth of the spectra was found to be relatively insensitive to wind direction, depending rather on significant wave height. But the magnitude of differential doppler (the difference in mean frequency between the horizontal and vertical spectra) is quite sensitive to the direction of the wind, having an observed upwind/downwind ratio of about two to one. Other dependencies on radar frequency and polarization are in general agreement with those found in 1970 by Valenzuela and Laing. (Author)