Tropical cyclone induced extreme wind, rainfall, and floods in the Mekong River Basin

Sammanfattning: Increasing magnitude and frequency of climate extremes under global warming are threatening the socioeconomic development in many parts of the world. The Mekong River Basin (MRB) is a good example for how climate extremes can affect society, as the transboundary MRB has experienced hydroclimate changes and fast socioeconomic development during the past decades. The MRB is a flood-prone area with high flood induced mortality, where heavy monsoon rainfall and tropical cyclones (TCs) landfall are the two main determinants of floods. This thesis focuses on change in TCs and their associated impacts on extreme wind, rainfall, and floods in the MRB. Findings from this thesis provide our knowledge and understanding of TCs and their impacts, which are needed to mitigate potential consequences of global warming in the MRB and other areas facing similar challenges. Employing reliable precipitation data, this thesis finds that TC induced rainfall plays a minor role in the annual mean precipitation in the MRB. But TCs are crucial to the occurrence of extreme rainfall events, especially at the eastern lower basin, where TCs can induce floods along their tracks. TC induced floods amount to 24.6% of all flood occurrence in the lower riparian countries. TC induced floods cause higher impacts on human mortality and displacement rates than the average of floods induced by all possible causes do. Moreover, future projection shows increases in the future TC intensity under the Representative Concentration Pathway (RCP) 8.5 scenario. Overall, this thesis reveals that climate extremes, such as TC associated rainfall and floods, can substantially affect society, in terms of high TC induced extreme rainfall and great human mortality and displacement rates caused by TC induced floods; and the projected future intensified TCs indicate increasing TC risks.