Impact of ocean resolution on SST over the Arabian Sea and Indian monsoon precipitation in a coupled GCM

Yoko Yamagami, University of Tokyo, Atmosphere and Ocean Research Institute, Tokyo, Japan, Masahiro Watanabe, University of Tokyo, Atmosphere and Ocean Research Institute, Bunkyo-ku, Japan and Hiroaki Tatebe, JAMSTEC Japan Agency for Marine-Earth Science and Technology, Research Center for Environmental Modeling and Application, Yokohama, Japan
Abstract:
We investigated, using a climate model called MIROC6 with two configurations (standard and eddy permitting ocean model referred to as “Subhires”), impacts of ocean resolution on simulating sea surface temperature (SST) in the Arabian Sea and Indian summer monsoon precipitation. In the Subhires model, mean cold SST biases over the Arabian Sea are mitigated owing to resolving the Red Sea and Persian Gulf that export warm water out to the Arabian Sea. The outflow is induced by meso-scale eddies and suppress the mixed-layer cooling by the upwelling off the Somalia-Oman coast. It is also found that high SST in the Arabian Sea leads to cyclonic atmospheric circulation over the northern Arabian Sea, which acts to increase precipitation over western India during summer. In addition, the Subhires is found to simulate a teleconnection from the monsoon rainfall better than the standard model. The teleconnection occurs at interannual time scale between the Indian summer monsoon rainfall variability and a descent over the eastern Mediterranean Sea, resulting from a monsoon-desert mechanism. The reason of this improvement in the Subhires model is discussed.
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