Schlimme, Ingo (2002) Der Einfluss von Kristallform und Grössenverteilungen auf die solare Strahlungsbilanz von Cirruswolken. (Diploma thesis), Christian-Albrechts-Universität, Kiel, Kiel, Germany, 84 pp.

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Abstract

The knowledge of ice crystal microphysical properties like crystal size, shape or number of crystal is important for the radiation balance destination for the remote sensing of cirrus clouds. At first the present work estimates the uncertainty of using different crystal shapes and crystal size distributions of cirrus clouds in radiative transfer calculations. The studies are based on the Monte Carlo radiative transfer model GRIMALDI, wich was advanced in the Institute of Marine Research. A plan-parallel homogeneous atmosphere with two various crystal shapes (hexagonal columns, irregular crystals) and 114 different crystal size distributions of in situ measurements serve as model input. Further more dicrete opitcal thicknesses form 0.5 to 12 and two solar zenith angles are considered. Spectral and broadband solar albedo, transmission and absorption features are calculated under the described requirements. The results display a precise dependency of broadband radiative flux densities of the used crystal size distributions. Variabilities occur in broadband absorption with a variation coefficient up to 25%, whereas the vacillations in upward and downward radiative fluxes (<10%) are smaller. Calculations vary severely in several spectral wavelengths. The choise crystal shape has got a greater impact on radiative fluxes than the varity of crystal size distributions. Another aim of this work is to examine the influence of inhomogeneity of clouds on radiation balance by using LIDAR-measurements of vvertical and horizontal extinction distributions. Different ways of model input determinations for the radiative transfer model show low deviation of the radiative fluxes. Finally, a funtional adjustment of optical thickness, wich results in the extinction profiles of LIDAR-measurements, as well as the calculated albedos, transmissions and absorptions are derivated.

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