Dipole Mode of the Precipitation Anomaly Over the Tibetan Plateau in Mid‐Autumn Associated With Tropical Pacific‐Indian Ocean Sea Surface Temperature Anomaly: Role of Convection Over the Northern Maritime Continent

Abstract

AbstractBased on observational data and numerical simulation results with the Community Atmosphere Model (CAM4), version 4 atmospheric general circulation model (AGCM), the influence of the sea surface temperature anomaly (SSTA) of the tropical Pacific–Indian Ocean mode (PIM) on the interannual variability of the Tibetan Plateau (TP) precipitation in mid‐autumn (October) is investigated. We find that the interannual variation of the mid‐autumn TP precipitation is characterized by a dipole mode with a southeast–northwest inverse pattern, which is influenced significantly by the large‐scale circulation anomalies induced by PIM. During a positive phase of PIM, that is, positive SSTA in both the tropical central‐eastern Pacific and western Indian Ocean accompanied by negative SSTA around the Maritime Continent, a robust lower‐level anticyclonic anomaly over the South Asia region (SAAC) and an upper‐level cyclonic anomaly over subtropical Asia are generated owing to the Rossby wave response to the suppressed convective heating over the northern Maritime Continent. As a result, the southerly (northerly) anomalies on the west (east) side of the SAAC can enhance (reduce) the transportation of moisture and the ascending motion over the northwestern (southeastern) TP. Meanwhile, the southward‐shifted East Asian westerly jet can further enhance the ascending motion over the northwestern TP by stimulating secondary circulation. Correspondingly, a positive (negative) precipitation anomaly appears over the northwestern (southeastern) TP. During a negative phase of PIM, the opposite case is also true. Therefore, the suppressed convective heating over the Maritime Continent serves as a pivotal medium by which PIM affects the TP precipitation in mid‐autumn.