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12/07 Lecture #1----Forcing and feedback of tropical circulation


Time: 2016-12-07 (Wednesday) 15:00-17:00
Speaker: Dr. MahyarMohtadi
Institution: MARUM – Center for Marine Environmental Sciences, University of Bremen
Venue: C2-403, Xi Ping Bldg
Hosts: Stephan Steinke and SelvarajKandasamy
Contact: Chen Jingyan, chenjy@xmu.edu.cn

Abstract: Climate models predict a slowdown of the zonal and meridional atmospheric overturning circulation over the tropics (the Walker and Hadley circulations) for the twenty-first century with severe consequences for tropical and global climate. However, debate exists on the appropriate interpretation of historical records and observations over the twentieth century, such as ENSO and the IOD, and necessitates longer records of past changes in tropical circulation to test the model results. Several records of continental rainfall, sea surface and thermocline temperatures extending back to the last glacial period suggest a stronger-than-today glacial zonal circulation in the tropics. Changes in the meridional circulation occurred through a number of forcings and feedbacks: while model simulations underscore the sensitivity of tropical circulation to temperature change, among other forcings, they remain equivocal and in part, inconsistent with proxy evidence. Untangling the (competing) impacts of meridional and zonal circulation changes on tropical hydroclimate, and whether and how these changes are reflected by different proxies at different sites, remains a critical task for both climate reconstructions and simulations.