The Role of Tropical Asian Landcover Disturbance in Altering Large-scale Circulations: Interaction with El Nino Southern Oscillation (ENSO) and the Asian Summer Monsoon

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Several recent papers have documented atmospheric circulation changes resulting from changing tropical land cover in climate model simulations. The proposed research focuses on elucidating the role of land cover changes in changing global circulation regimes and the interactions between the effects of land cover change and other modes of variability including El Nino southern oscillation (ENSO) and the Asian summer monsoon through a variety of general circulation model simulations. The PIs address the following main hypotheses:1) Historical land cover changes in the tropics and in Southeast Asia, in particular, cause similar magnitude circulation changes as seen in the alternating phases of ENSO. By affecting the tropical divergent circulation, these changes have global reach. 2) Tropical land cover changes cause shifts in tropical circulations which would tend to enhance the El Nino phase of ENSO at the expense of La Nina.3) Circulation changes due to land cover change and those due to ENSO interact non-linearly.4) Circulation changes due to tropical land cover changes may have a role in explaining the observed decreased anticorrelation between El Nino and the Indian summer monsoon. The PIs will examine these hypotheses with ensemble general circulation model simulations and observational analysis of circulation changes due to tropical land cover changes; changes due to El Nino-like SST anomalies and circulation changes due to a combination of both effects. Broader Impacts: This research adds significantly to previous studies of the effect of land cover change and addresses two large, outstanding questions (intellectual merit) with broader impacts in promoting interdisciplinary research, and societal implications including the prediction of regional monsoon variability and the expression of expected CO2 induced global warming.This project is supported under the Climate Variability and Predictability Program (CLIVAR).