The research presented in this thesis involves the study of ice cloud microphysical and optical properties using both hyperspectral and narrowband infrared spectral data. First, ice cloud models are developed for the Infrared Atmospheric Sounding Interferometer (IASI) instrument onboard the METOP-A satellite, which provide the bulk-scattering properties of these clouds for the 8461 IASI channels between 645 and 2760 cm-1. We investigate the sensitivity of simulated brightness temperatures in this spectral region to the bulk-scattering properties of ice clouds containing individual ice crystal habits as well as for one habit distribution. The second part of this thesis describes an algorithm developed to analyze the sensitivity of simulated brightness temperatures at 8.5 and 11.0 µm to changes in effective cloud temperature by adjusting cloud top height and geometric thickness in a standard tropical atmosphere. Applicability of using these channels in a bi-spectral approach to retrieve cirrus cloud effective particle size and optical thickness is assessed. Finally, the algorithm is applied to the retrieval of these ice cloud properties for a case of single-layered cirrus cloud over a tropical ocean surface using measurements from the Moderate Resolution Infrared Spectroradiometer (MODIS). Cloud top height and geometric thickness in the profile are adjusted to assess the influence of effective cloud temperature on the retrieval.

The research presented in this thesis involves the study of ice cloud microphysical and optical properties using both hyperspectral and narrowband infrared spectral data. First, ice cloud models are developed for the Infrared Atmospheric Sounding Interferometer (IASI) instrument onboard the METOP-A satellite, which provide the bulk-scattering properties of these clouds for the 8461 IASI channels between 645 and 2760 cm-1. We investigate the sensitivity of simulated brightness temperatures in this spectral region to the bulk-scattering properties of ice clouds containing individual ice crystal habits as well as for one habit distribution. The second part of this thesis describes an algorithm developed to analyze the sensitivity of simulated brightness temperatures at 8.5 and 11.0 µm to changes in effective cloud temperature by adjusting cloud top height and geometric thickness in a standard tropical atmosphere. Applicability of using these channels in a bi-spectral approach to retrieve cirrus cloud effective particle size and optical thickness is assessed. Finally, the algorithm is applied to the retrieval of these ice cloud properties for a case of single-layered cirrus cloud over a tropical ocean surface using measurements from the Moderate Resolution Infrared Spectroradiometer (MODIS). Cloud top height and geometric thickness in the profile are adjusted to assess the influence of effective cloud temperature on the retrieval.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

The feedback between clouds and sea ice got more importance in the last years, because of the declining Arctic sea ice extent. Previous observations show the formation of low clouds over newly formed open water. These low clouds are very important for the Arctic Energy Budget, because they warm the surface. This leads to increasing temperatures and stronger sea ice loss. To assess the relationship between sea ice cover and cloudiness, satellite observations by DARDAR were compared with both global climate reanalyses ERA–Interim and MACC. The analysis focuses on 2007 – 2010 and the relationship between different parameters from the different datasets. It is found that the reanalyses only poorly approximate the cloud cover in the Arctic. Consequently no strong correlation was found for the time period 2007 – 2010. / Das Wolken–Albedo–Feedback in der Arktis gewann in den letzten Jahren immer mehr an Bedeutung aufgrund des Rückganges der Meereisfläche. Vorhergehende Arbeiten zeigten die Bildung von tiefer Bewölkung über kürzlich aufgebrochenen Meereisstellen. Diese tiefen Wolken sind sehr wichtig für das arktische Energiebudget, wegen des Erwärmens der Oberfläche. Daraus folgt ein Anstieg in der bodennahen Temperatur und ein verstärkter Rückgang des Meereises. Um den Einfluss der Meereiskonzentration auf die Wolkenbildung zu untersuchen, werden in dieser Arbeit Satellitendaten von DARDAR mit den beiden globalen Klimareanalysen Era–interim und MACC verglichen. Analysiert werden Daten aus den Jahren 2007 bis 2010 und für verschiedene Oberflächenbedingungen werden Korrelationen der einzelnen Datensätze erstellt. Es hat sich gezeigt, dass die Darstellung der Wolkenbedeckung in der Arktis durch die Reanalyse Daten nicht geeignet ist. Aus diesem Grund wurden keine signifikanten Korrelationen in der Zeitspanne von 2007 bis 2010 gefunden.

Not available / text

Not available / text

科学研究費補助金 研究種目:一般研究(C) 課題番号:63540311 研究代表者:石坂 隆 研究期間:1988-1989年度