Retrieval of latent heat flux and longwave irradiance at the sea surface from SSM/I and AVHRR measurements

Abstract A combination of passive microwave measurements from the Special Sensor Microwave/Imager (SSM/I) with infrared imagery from the Advanced Very High Resolution Radiometer (AVHRR) is used to derive flux densities of latent heat and longwave radiation at the sea surface. While the AVHRR measurements are used to derive the surface skin temperature of the ocean the SSM/I observations are analysed for the retrieval of the surface wind speed, the near-surface atmospheric humidity and the downwelling longwave irradiance. Radiative transfer calculations are carried out for the simulation of the radiometer signals and for the computation of the radiative fluxes at the sea surface for a large set of globally distributed atmospheric/oceanic situations which have been collected from historical radiosonde and surface observations. The simulations are used for the development of retrieval models and for the estimate of error budgets. Subsequently, the derived techniques are applied to real satellite data and the retrieved fluxes are compared to surface observations from the operational meteorological network as well as from special field measurements which have been taken during the Coupled Ocean Atmosphere Response Experiment and the Central Equatorial Pacific Experiment in the equatorial Pacific Ocean. The comparisons demonstrate accuracies of 30 W/m2 for the latent and longwave fluxes when single satellite soundings are used. Monthly averages of the fluxes can be obtained from the satellite measurements with an accuracy better than 10 W/m2.

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