Synergic Use Of Microwave And Infra-red Radiornetry For Cloud Analysis

Introduction The classification of clouds and the evaluation of liquid water content interest meteorology and climate modelling from space. Many methods have been developped using either optical measurements (1) or microwave radiometers (2). But the number of simultaneous use of both techniques remain poor partly due to the problem of coincidence in time and place of the two kinds of measurements (3). Using microwave radiometry it is quite difficult to establish and validate a liquid water retrieval algorithm due to the lack of in-situ measurements, so a comparison to liquid water content obtained by optical method is interesting. The optical approach takes into account the fact that the reflectance is a function of the albedo itself related to the optical depth. Moreover combining infrared and visible (or near-visible) channels enables a cloud classification which can help to develop microwave algorithm. This preliminary study takes benefit of the exactly coincident measurements in time and location of the micowave radiometer (ATSWMWR) and infrared instrument (ATSRAR) aboard ERS1, to compare the results of optical and microwave approaches on some images acquired in July 1992.