RADIATIVE TRANSFER CHARACTERISTICS OF 89GHz MICROWAVE IN THE PRESENCE OF CLOUDS OVER LAND

Abstract

 The utilization of satellite microwave (MW) observation is essential to understand the long-term and extensive cloud water content (CWC) distribution. Over highly heterogenous land, understanding of radiative transfer characteristics between land and atmosphere including clouds is important, but those are not elucidated. In this study, based on radiative transfer theory which covers land and atmosphere, we first clarify the important variables for radiative transfer between land and atmosphere under existence of clouds. Then, as base information for estimation of CWC over land using MW, we utilized in-situ observation and simulation to analyze the land emission, atmospheric downward radiation, and land emissivity. As a result, contrary to the commonly held image of being very complicated, we revealed that with downward radiation from thick clouds, especially exceeding 2kg/m2, the heterogeneity of emissivity can be reasonably negrected, because downward radiation becomes close to the physical temperature of land surface.