On using significant wave height and radar cross section to improve radar altimeter measurements of wind speed

Wind blowing across the ocean surface generates small, centimeter scale roughness. The radar cross section (RCS) measured by spaceborne, nadir-looking altimeters operating at about 13.5 GHz is responsive to this roughness. Present altimeter algorithms use RCS to infer wind speed. We compare Geosat altimeter estimates of wind speed and nearly coincident estimates from NOAA data buoys to determine whether altimeter algorithms can be improved by using more of the information available from altimetry. We find that a marginal improvement in wind speed retrievals can be obtained by including additional RCS information and significant wave height in the retrieval algorithm. Perhaps most important, results also suggest that wind-wave growth is suppressed in the presence of preexisting ocean swell.

[1]  Jin Wu.  Effects of long waves on wind boundary layer and on ripple slope statistics , 1977 .

[2]  G. Geernaert,et al.  Variation of the drag coefficient and its dependence on sea state , 1986 .

[3]  Frank Monaldo,et al.  Expected differences between buoy and radar altimeter estimates of wind speed and significant wave height and their implications on buoy‐altimeter comparisons , 1988 .

[4]  J. Gower,et al.  Satellite altimeter measurements of sea state—An algorithm comparison , 1979 .

[5]  T. Barnett,et al.  Measurements of wind-wave growth and swell decay during the Joint North Sea Wave Project (JONSWAP) , 1973 .

[6]  D. Barrick,et al.  Wind dependence of quasi-specular microwave sea scatter , 1974 .

[7]  F. Riedel,et al.  Proposed Model for the Elevation Spectrum of a Wind-Roughened Sea Surface , 1979 .

[8]  G. Brown,et al.  Backscattering from a Gaussian-distributed perfectly conducting rough surface , 1978 .

[9]  David B. Gilhousen,et al.  A Field Evaluation of NDBC Moored Buoy Winds , 1987 .

[10]  Gary S. Brown,et al.  Estimation of surface wind speeds using satellite‐borne radar measurements at normal incidence , 1979 .

[11]  Jin Wu,et al.  Sea‐Surface Slope and Equilibrium Wind‐Wave Spectra , 1972 .

[12]  W. Pierson,et al.  A proposed spectral form for fully developed wind seas based on the similarity theory of S , 1964 .

[13]  W. Campbell,et al.  Southern ocean mean monthly waves and surface winds for winter 1978 by Seasat radar altimeter , 1983 .

[14]  W. Munk,et al.  Measurement of the Roughness of the Sea Surface from Photographs of the Sun’s Glitter , 1954 .

[15]  N. Draper,et al.  Applied Regression Analysis , 1966 .

[16]  Donald E. Barrick,et al.  Rough Surface Scattering Based on the Specular Point Theory , 1968 .

[17]  P. Deleonibus.  Momentum flux and wave spectra observations from an ocean tower , 1971 .

[18]  Julius Goldhirsh,et al.  Validation of Geosat altimeter‐derived wind speeds and significant wave heights using buoy data , 1987 .

[19]  Frank J. Wentz,et al.  Further development of an improved altimeter wind speed algorithm , 1986 .