Einfluss der atlantischen Meeresoberflächentemperatur auf Niederschläge in Indien und dem Sahel im Kieler Klimamodell
The Sahelien and Indian rainfall is part of climate research for many years. There where wet and dry periods in the Sahel and India in the last century, whose circumstances are not cleary detected, but the observations show a similar timeseries of the Atlantic Multidecadal Variability (AMV) and the...
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| Format: | Thesis |
| Language: | German |
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2012
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| Online Access: | https://oceanrep.geomar.de/id/eprint/19981/ https://oceanrep.geomar.de/id/eprint/19981/1/938677_Ba_MHell.pdf |
| Summary: | The Sahelien and Indian rainfall is part of climate research for many years. There where wet and dry periods in the Sahel and India in the last century, whose circumstances are not cleary detected, but the observations show a similar timeseries of the Atlantic Multidecadal Variability (AMV) and the rainfall over the Sahel and India. The aim was to investigate if these periods could be part of internal climate variability. A 4200 years control run of the Kiel Climate Model was used to analyze the internal precipitation and sea surface temperature variability. All data had been low-pass filtered with a 10 years cutoff-frequency and reduced to summer means to focus on multidecadal scales. EOF-Analyses and box-mean has been taken for further analyses. The spectrums of the timeseries show significant multidecadal periods of about 80 and 500 years in the AMV and shorter periods of about 40 years in the Pacific Decadal Oscillation (PDO). These frequencies can partly be seen in the spectrum of the indian rainfall, but not in the spectrum of the Sahelian rainfall. It gets clear, that the monsoon rainfall systems in Africa and India have variability in common, that means, that there are periods of more rainfall in all monsoon areas. A reason for this is perhaps a shift of the Intertropical Convergence Zone (ITCZ) in the boreal summer. An influence of the North Atlantic Ocean cannot be seen in sahel nor in indian rainfall variability. This is a major difference to the observations. Instead, there seems to be a strong influence of the equatorial Oceans on both rainfall areas. A very strong relationship is found between the Sahel and the Equatorial West Atlantic and between India and the Equatorial Central West Pacific. A surprising result is a very significant relation between the PDO and the monsoon rainfall over India. The significant result shows, that more rainfall over India is related to a positive PDO-period. If this is connected because the influence of the Pacific on the Indian Ocean or because the shift of the ... |
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