Wassmann, Andreas (2008) Mikrowellenradiometrie auf See. (Diploma thesis), Christian-Albrechts-Universität, Kiel, Germany, 107 pp.

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Abstract

Remote sensing of the atmosphere in the microwave part of the electromagnetic spectrum plays a major role in field of remote sensing, both in satellite-borne and in ground-based. To obtain a high vertical resolution in the lower part of the troposphere and especially in the boundary-layer the ground-based remote sensing figured out as well suitable. Here, passive microwave radiometers are utilized to measure the water vapor content in an atmospheric column, the IWV (Integrated Water Vapor), as well as cloud liquid in a column of a cloud, the LWP(LiquidWater Path). By adding certain frequencies temperature and humidity profiles can be obtained parallel. Such techniques are applied on solid ground. In this work the offshore operation of a multi-channel microwave radiometer on board a vessel, RV Polarstern, is investigated and the retrieval algorithms are adjusted to maritime conditions. Besides, the radiometer is operated on two transect cruises from the southern to the northern hemisphere and vice versa. The utilized radiometer is a HATPRO radiometer (Humidity And Temperature PROfiler), manufactored by the Radiometer Physics company in Meckenheim, Germany. Applying a filterbank receiver, all 14 frequencies used by the radiometer are scanned parallel along the absorption lines of water vapor (22.2 GHz to 31.4 GHz) and the absorption lines of oxygen (51.2 GHz to 58 GHz). Along these lines the thermal emission of the atmosphere is measured. Scanning parallel yield a high temporal resolution. Further technical details of the HATPRO and the mode of operation are given in chapter 3. By means of retrieval algorithms temperature and humidity profiles, as well as IWV and LWP are calculated from the thermal emission. The computation of such algorithms as well as the necessity of different algorithms for different climatic regions is described in chapter 4. For that, a radiative transfer calculation is carried out to simulate the thermal emission from radiosonde data. With the obtained data the retrieval algorithms are then calculated using quadratic regressions. The theoretical background of radiative transfer calculation is given in chapter 2. The resulting algorithms yield a better performance than the provided, especially in lower latitudes. The application to raw data of the two transects is shown in the cross sections of the temperature and the relative humidity as well as the meridional distribution of IWV and LWP along the course track in chapter 6. Further applications of the HATPRO onboard a vessel lead to a climatology of atmospheric profiles of temperature, humidity and the distribution of IWV and LWP.

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