Variation of Anomalous Convergence Around Kalimantan Island in Lower Troposphere and Its Role in Connecting the East Asian Summer Monsoon and Australian Winter Monsoon

Abstract

AbstractUsing the data from ERA‐interim, the Hadley Centre Global Sea Surface Temperature data set, and the Climate Prediction Center Merged Analysis of Precipitation, after removing the simultaneous El Niño and Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) signals, we have investigated variations of anomalous convergence around Kalimantan Island in lower troposphere in associations with the East Asian summer and Australian winter monsoons. Results indicate that when negative sea surface temperature anomalies appear in the western Pacific on both sides of the equator, the atmospheric cooling over the northwestern Pacific and from the South Pacific Convergence Zone (SPCZ) to Australia is favorable for the maintenance of anticyclonic anomalies over the areas from the western Pacific to the South China Sea and from the south of the equator to the northeast of Australia. These anomalous anticyclonic circulations can induce equatorial easterly anomalies, which subsequently facilitate the maintenance of anomalous convergence around Kalimantan Island. In turn, the anomalous convergence in Kalimantan Island is favorable for the maintenance of anomalous anticyclonic over the northwestern Pacific and SPCZ and thereby intensifies both the western Pacific subtropical high and the Australian High, inducing concurrent intensifications of the East Asian summer monsoon and Australian winter monsoon. Related to the anomalous convergence over Kalimantan Island, precipitation and temperature decrease from the western Pacific to SPCZ but increase from the Indian Ocean to western Maritime Continent and Australia, while temperature is lower than normal in Kalimantan. The above results have remarkable implications for in‐depth understanding of the mechanism behind anomalies of the East Asian summer monsoon and Australian winter monsoon.