Large-scale circulation dominated precipitation variation and its effect on potential water availability across the Tibetan Plateau

The large-scale circulation, Indian summer monsoon (ISM), has a strong influence on the Tibetan Plateau (TP) since its onset and intensity have profound impacts on regional precipitation, which then can supply water for glaciers, lakes, rivers and social demands. Weakening monsoon intensity and longer monsoon duration seem contradictory, as a weaker monsoon tends to produce less precipitation, while a longer duration increases the probability of precipitation. Past research has focused on how ISM's intensity affects precipitation, with little consideration of the impacts of ISM duration. Here, we investigate the long-term (1979-2100) variability in the ISM's duration and intensity. We find a prolonged ISM from 1979 to 2018, accompanied by monsoon weakening. Different combinations of duration and intensity have resulted in different spatial patterns of precipitation across the southeastern TP. Weakening and prolonged ISM is helpful to produce more precipitation around the southeastern TP, with intensity acting as a dominant control. Afterwards, an obvious impact can be found on potential water availability. Climate projections suggest that the ISM will weaken and lengthen until 2100, thereby increasing precipitation and potential water availability across the southeastern TP. This long-term trend should receive more attentions as increased regional extreme precipitation will increase the probability of flood risks until the end of this century.