Retrieval of microwave surface emissivities using multi-sensor satellite remote sensing

The retrieval of surface microwave emissivity can be subject to significant errors due to the contributions from atmospheric emission and absorption. These errors, which depend on both the surface microwave emissivity and atmospheric water vapour content, can be more than 0.1. The errors will affect the interpretation of the geophysical parameters based on the surface microwave emissivity, for example soil moisture, surface roughness and vegetation cover, which are of interest for global change studies and other applications. The authors present a new technique for correcting brightness temperature measurements and retrieving the microwave surface emissivity. The method uses simultaneous measurements from the ERS-1 microwave and infrared radiometers. Radiative transfer simulations using a microwave atmospheric model incorporating a North Atlantic range of atmospheres show that the surface microwave emissivity can be retrieved to an accuracy of 0.001 r.m.s. for atmospheres less than 2.5 gm/cm^-3 in water vapour content. A validation study of the technique over the ocean is presented and possible sources of residual error are discussed