Die Veränderungen des Luftdrucks im IPCC A1B Szenario: Mittlerer Zustand und Muster der Variabilität

Sea level pressure (SLP) is an important meteorological and climatological parameter, which gives information about the state of the atmospheric circulation. In this Diploma thesis, an investigation of changes in the mean state and patterns of variability of SLP is presented, with special scope on changes in the patterns of variability. For this analysis a multi model ensemble of 23 climate models for 20C3M and A1B scenario of the IPCC is used. In these simulation of a warming climate the mean SLP increases over the tropical Indo-Pacific region and decreases over the tropical Atlantic region. It could be shown, that there is a strong contrary linkage between the temperature change of the air column and the SLP change in the tropics. In the extratropics of both hemispheres an increase in SLP over the subtropics and a decrease over the polar regions is detected. As in former studies a strong link between extratropical SLP response and the positive trend in the Arctic Oscillation (AO) in the northern hemisphere (NH) and the Southern Annular Mode (SAM) in the southern hemisphere was found. In addition it could be demonstrated in this thesis that a part of the SLP change in the arctic, especially near the Aleutian islands, is due to a positive trend in the Pacific North American (PNA) pattern. It could be shown, that these changes are related to an increase in the jet stream windspeed, which are caused by the strong warming in the upper tropical troposphere, that influences the large scale circulation. The patterns of variability were obtained with an Empirical Orthogonal Functions (EOF) analysis, and with the new Distinct Empirical Orthogonal Functions (DEOF) analysis are those patterns determined, which strongest gain or lose relevance in climate change. In EOF analysis the explained variance of the dominant mode decreases in both hemispheres in summer. The result of the DEOF analysis can illustrate, that in boreal summer the AO weakens over Greenland, the North Atlantic and the Northeast Pacific and in austral summer the SAM loses relevance over the Ross Sea and tightens further to the south. In winter the explained variance of the dominant mode increases in both hemispheres and the result of the DEOF Analysis in the SH is, that the SAM strengthens over the Ross Sea, the South Atlantic, the Southeast Pacific and the region south of Australia. In the NH the DEOF analysis shows, that a pattern with one pole over the Northeast Pacific and a second pole over the Arctic gets the most important pattern in 21C. This pattern shows changes in the AO as well as in the PNA. A DEOF analysis of geopotential height in different levels can reveal, that the same pattern can be found in the entire troposphere (up to 200 hPa) and that the pole of the pattern over the Arctic extents into the stratosphere. This is a hint, that there could be a connection between the changes of SLP and the changes in the stratosphere.With a composite analysis it was obtained, that during positive PNA Phase the Aleutian low deepens and extends further into the east and that during negative PNA Phase the SLP increases over the Northeast Pacific, i.e. that there is a strengthening of the blocking in this region