11:15 〜 11:30
[U03-08] The critical role of the westerlies in past and future East Asian Summer Monsoon
★Invited Papers
キーワード：Monsoon, Westerlies, Rainfall
The East Asian Summer Monsoon is unique amongst summer monsoonal systems in its spatial structure 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 explore the 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 paleoclimate variations and observed modern-day variability. For future climate, the influence of the westerlies leads to marked intensification of the East Asian rainband during the pre-Meiyu stage, because of stronger westerlies impinging on the Tibetan Plateau during this time of the year.