Radar determination of winds at sea

Analysis of C and Ku band ocean backscatter measurements under low‐wind conditions

“…Scatterometers measure the normalized radar cross section (NRCS), rr ø, of the ocean surface to infer ocean surface wind speeds and directions [Moore, 1979]. The NRCS at intermediate incidence angles and microwave frequencies is related to the spectral density of capillary and short gravity waves, which in turn is strongly correlated to the surface winds.…”

Sea Wind Measurement by Doppler Navigation System with X-Configured Beams in Rectilinear Flight

“…DNS in the mode of the multi-beam scatterometer should use the horizontal transmitting and receiving polarization, which provides a greater difference between the upwind and downwind NRCS values than the vertical transmitting and receiving polarization [4,7,36]. As the range of typical mounting angles of a beam axis in the vertical plane (15 • to 30 • ) is not so far from nadir, the highest incidence angle from this range should be used to provide better usage of the anisotropic properties of water surface scattering at medium incidence angles [35].…”

“…The directions of the DNS beams 1, 2, 3, and 4 relative to the aircraft course are ψ 0.a.1 , ψ 0.a.2 , ψ 0.a.3 , and ψ 0.a. 4 , respectively ( Figure 1). Let the wind and wave field be uniform over the scene and the sea-surface wind blow in direction ψ w , the angle between the up-wind direction and the aircraft course ψ be α, and the NRCS model function for medium incidence angles follows Equation (1).…”

“…A number of successful airborne and platform scatterometer experiments performed for a study of water surface backscattering, its dependence on both the incidence and azimuth angles, frequency, polarization, wind speed, and direction [4,[6][7][8]10,18] allowed the development of appropriate geophysical model functions, and to further use them for wind retrieval by satellite and airborne scatterometers. Experimental airborne wind measurements by a scatterometer are typically performed in either circular track flight using a fixed fan-beam antenna or in rectilinear track flight using a rotating antenna.…”

C-band Scatterometers and Their Applications

“…The concept of retrieving wind speed at sea surface from the radar backscatter goes back to the Second World War. During the World War II, marine radar operators observed disturbing noises, called "clutter", on their radar screens, which made them difficult detecting targets on the ocean surface (Moore et al, 1979). The clutters were the backscatter of the radar pulses from the small waves on the sea surface.…”