Interdecadal variation of Indian Ocean basin mode and the impact on Asian summer climate.

This study documents an interdecadal variation in the pattern of Indian Ocean basin mode (IOBM) of sea surface temperature (SST) during boreal summer, where the center of action in the IOBM shifted towards the Arabian Sea after the late 1970s. Correspondingly, the influences of an interannual warming in the tropical Indian Ocean on the Asian summer climate became more significant after the late 1970s due to the Arabian Sea center of action, which are characterized by anomalous subsidence and anticyclones over the Bay of Bengal and the South China Sea. These atmospheric anomalies may result in surface temperature and precipitation anomalies in a wide area of Asia. Numerical experiments demonstrate the different influences of different IOBM patterns on the Asian summer climate. Statistical analysis and numerical experiments indicate a minor role of the different tropical Pacific SSTs concurrent with the different IOBMs in causing the different Asian summer climate anomalies. Plain Language Summary: The year‐to‐year warming/cooling in the tropical Indian Ocean can notably influence the atmospheric circulation over Asia via air‐sea interaction and atmospheric dynamic process. The current study reveals a shift of the center of action in the year‐to‐year warming/cooling of tropical Indian Ocean during boreal summer after the late 1970s, where this center of action was mainly situated in the southern tropical Indian Ocean during 1951–1979 and this center of action shifted towards the Arabian Sea during 1981–2016. Our results suggest that this shift of center of action in the year‐to‐year warming/cooling of tropical Indian Ocean may exert an important impact on the Asian summer climate. In comparison to 1951–1979, during 1981–2016, more significant surface temperature and precipitation anomalies occurred in Asia corresponding to a year‐to‐year warming/cooling in the tropical Indian Ocean due to the Arabian Sea center of action. Numerical experiments show similar results. The findings of this study indicate that different patterns of tropical Indian Ocean warming/cooling may result in different climate anomalies in Asia, which provides a better understanding of the complex mechanism of the interaction between the tropical Indian Ocean and the Asian climate. Key Points: The center of action in the Indian Ocean basin mode (IOBM) shifted towards the Arabian Sea during boreal summer after the late 1970sThe Asian summer climate is more significantly affected by the IOBM after the late 1970s due to the Arabian Sea center of actionThe concurrent tropical Pacific SSTs have less impact on the shift of Asian summer climate anomalies associated with the shift of IOBM [ABSTRACT FROM AUTHOR]