Estimation of Ocean Surface Wind Speed and Direction From Polarimetric Radiometry Data
LONG-TERM GOALS To develop improved methodologies for estimating ocean surface wind vectors from polarimetric microwave radiometry data. OBJECTIVES To evaluate a proposed algebraic method for correcting microwave radiometry data for atmospheric effects, and for estimating the wind speed and direction from the corrected data. APPROACH Various combinations of the vertically and horizontally polarized brightness temperatures have been examined, using simulations based on a two-scale model
... cale model (Lyzenga, 2006) , in order to determine their dependence on the atmospheric water vapor and liquid water content as well as the surface wind speed. These predictions are compared with actual WindSat data, and used to provide an indication of the wind speed that is independent of atmospheric conditions. A second set of equations is used to calculate the wind direction from the third and fourth Stokes parameters. WORK COMPLETED A wind vector algorithm has been proposed on the basis of two-scale simulations, and preliminary tests have been carried out two WindSat data sets. Several additional data sets have been acquired and are currently being used to further test and refine the proposed algorithm. RESULTS Plots of the simulated brightness temperatures over a range of wind speeds and atmospheric variables are shown in Figure 1 . The ratio R = (T v ̵ T vo )/(T h ̵ T ho ) was found on the basis of these simulations to be nearly independent of atmospheric effects, and to be linearly related to the wind speed. Plots of R versus the wind speed are shown in Figure 2 .