Recent Research Advances on the Interannual-interdecadal Variations of Drought/Flood in South China and Associated Causes

Based on changes of spatial-temporal distribution of flood and drought in South China under global warming, the recent research progress on characteristics of inter-annual and inter-decadal variations of drought/flood and associated causes are reviewed. It's found there will be less precipitation in South China especially for the Yangtze valley in the developing phase of El Niño, while more precipitation in the decay phase. During the above process, the basin wide warming in tropical Indian Ocean are found to intensify the Northwestern Pacific subtropical high and shift it to a more southward position, leading to the occurrence of low-level anticyclone circulation over Northwestern Pacific, which would affect the precipitation of South China through adjusting the southerly and moisture transportation. The snow cover of the Tibet Plateau is also found as a key factor, when more snow cover occurs in spring-winter, the sensible heat flux is too weak to heat troposphere, which would reduce the meridional temperature gradient to cause a weak summer monsoon and more precipitation over the Yangtze valley, and vice versa. For synergistic effects of multi-factors on the occurrence of flood and drought in South China, results indicate it's impacted by multiple factors and cannot be dominated by one single factor. For example, the Philippine anticyclone can be impacted by the winter Tibet Plateau snow cover, El Niño and basin wide warming of tropical Indian Ocean. For the inter-decadal variation of the inter-annual relationship between flood and drought in South China and their influencing factors, strong inter-decadal variation on the relationship between the influencing factors and flood/drought are found, when these factors exhibit a strong inter-decadal variation. For example, the relationship between tropical Pacific Ocean and South China precipitation is found loose in recent decades, while the influence of Indian Ocean sea surface temperature anomaly on South China is intensified. Based on the aforementioned results, it suggests more attentions being focused on the prediction strategy and method for South China to improve the predictability of drought and flood.