Atmospheric Absorption Models for the Millimeter Wave Range

Abstract

This thesis deals with absorption models of water vapor, oxygen and nitrogen which are part of the Atmospheric Radiative Transfer System, ARTS, which is a joint development of the Department of Radio and Space Science, Chalmers University of Technology, Göteborg and the Institute of Environmental Physics, University of Bremen. ARTS is designed to be used in remotely sensed data analysis. Since the absorption models are embedded in the broader frame of the radiative transfer equation, the main physical concepts of the transfer of electromagnetic radiation through the Earth´s atmosphere are discussed. Furthermore a theoretical basis of absorption and emission processes in connection with molecular rotational transitions is outlined. After the theoretical part a detailed comparison of differentabsorption models is performed which are presently used operationally in remote sensing data analysis. This comparison concentrates on models for oxygen, nitrogen, and water vapor especially for the frequency range of 1-1000GHz. In a next step a new water vapor absorption model, named AAM02, for the 1-1000GHz frequency range is built up. AAM02 uses for the H2O-line absorption term various data bases while the continuum absorption term is fitted to laboratory data. The AAM02 and other water vapor absorption models are then compared to different laboratory and free atmosphere measurements.A summary and conclusions complete this work.