PAOC Colloquium: John Chiang, UC Berkeley
Role of Seasonal Transitions and the Westerlies on the Rainfall Climate of East Asia
The East Asian Summer Monsoon is unique amongst summer monsoonal systems in in northward extent as well as in its complex seasonality, exhibiting dynamically distinct rainfall stages and abrupt transitions between them. Previous studies have alluded to the seasonally-varying downstream influence of the westerlies flowing around the Tibetan Plateau as central to the rainfall seasonality. I propose a hypothesis that the East Asian summer rainfall variability and change arise through modulation in the meridional position of the westerlies impinging on the Plateau, which in turn altered the timing and duration of its seasonal transitions. The viability of this hypothesis is demonstrated through examples from observed modern-day variability and from paleoclimatic changes. I will end with a discussion on the basic ingredients controlling East Asian summer monsoon seasonality.