PAOC Colloquium - John Chiang (UC Berkeley)

John Chiang, UC Berkeley
Monday, May 22, 2017 - 12:00pm to 1:00pm

"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 inuence of the westerlies owing 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.

About the Speaker

My research focuses on large-scale tropical atmosphere-ocean (and increasingly, land) systems and its interactions with the global climate. My early work was on the large-scale convective climate of the tropical Atlantic, which possesses a remarkable property of being exquisitely sensitive to change; and in changing, become agents of climate change elsewhere. It got me to thinking about the larger role the tropics play in the global climate system, in particular the way it responds to, and feeds back on, climate forcing. This line of questioning has led me to consider ocean-atmosphere interactions in different ocean basins, and the interactions between them; to interactions between the extratropics and tropics, focusing on processes as far removed as the thermohaline circulation, and building ice sheets. Past climate change motivate much of my research, as it offers valuable clues on the linkages between various climate processes and just how susceptible our climate is to change. My ultimate goal is to understand how the global climate reorganizes in the face of climate forcings, past and future; while that goal is still in the far distance, all signs point to the tropical climate as key.


About this Series

The PAOC Colloquium is a weekly interdisciplinary seminar series that brings together the whole PAOC community. Seminar topics include all research concerning the physics, chemistry, and biology of the atmospheres, oceans and climate, but also talks about e.g. societal impacts of climatic processes. The seminars take place on Monday from 12-1pm in 54-923. Lunch is provided after the seminars to encourage students and post-docs to meet with the speaker. Besides the seminar and lunch, individual meetings with professors, post-docs, and students are arranged. 2016/2017 co-ordinators: Tom Beucler (, Deepa Rao (, Madeleine Youngs ( and Catherine Wilka (