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Abstract:
The surface heating on the Tibetan Plateau (TP) exerts large influence on the Asian summer monsoon. Drivers of TP surface heat include tropical forcings and other climate modes in middle and high latitude of the Northern Hemisphere, however whether the climate modes in Southern Hemisphere influence the TP surface heat is rarely studied. Using multiple source data diagnosis and numerical experiment from an atmospheric general circulation model (AGCM), we found that the Antarctic Oscillation (AAO) in May can efficiently modulate the subsequent surface heat source over the TP in June. When the AAO is in positive phases, a northeastward propagating atmospheric Rossby wave train originates from the Amundsen Sea low. As a part of this wave train, a pair of anomalous cyclone and anticyclone in the Southern Hemisphere accelerates the surface southeasterlies between them, accompanied by cold sea surface temperature (SST) anomaly in the equatorial middle and eastern Indian Ocean induced by the wind evaporation-SST feedback. Due to the large thermal inertia, in June, the cold SST anomaly stimulates anticyclone anomalies over the western TP and eastern Arabian Sea, which increase the moisture transportation toward the TP and are conducive to the formation and maintenance of the precipitation over the middle and eastern TP. In contrast, the surface heat source, which is dominated by the upward sensible heat flux, is reduced substantially. This result indicates that the AAO can be one of the precursors of the TP heat source, and may help improve the prediction of the Asian summer monsoon.
