East African hydroclimate variability and its interactions with the Indian Ocean over the last millennium
(2016)
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- Authors
- Supervisors
- Goosse, Hugues
- Abstract
- The East African rainfall is characterized by a strong interannual variability, currently superimposed on a (multi-)decadal drying trend. While observations collected over the last decades show that the East African rainfall correlates positively with the western Indian Ocean sea-surface temperatures and negatively with the eastern Indian Ocean sea-surface temperatures, the physical processes involved and the stability of those teleconnections over time are not well known. Hence, this thesis aims to improve understanding of how sea-surface temperatures in the Indian Ocean are linked to the East African rainfall variability at the interannual to the multi-decadal time scale. This is achieved through the analysis of the simulations performed by several climate models. Various complementary methodologies are used in order to minimize the potential impact of climate models biases on our results. Based on model-data comparison, we suggest that the changes in East African hydroclimate and their link to the Indian Ocean sea-surface temperature are driven at the interannual time scale by natural variability rather by external forcings over the last millennium. Using a data assimilation scheme, we demonstrate that the observed covariance between the East African rainfall and the Indian Ocean sea-surface temperatures has the potential to improve the regional to large-scale reconstructions of both variables, although biases in the physics of current climate models prevent obtaining such skillful reconstructions. Sensitivity experiments with the climate model EC-EARTH show that the Indian Ocean surface is indeed an important driver for the East African rainfall variability at the interannual time scale, through its influence on the atmospheric circulation.
- Affiliations
Citations
Klein, F. (2016). East African hydroclimate variability and its interactions with the Indian Ocean over the last millennium. https://hdl.handle.net/2078.5/179747