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Abstract:
Extreme weather and climate events such as torrential rainfalls and heat waves over Asia and Europe are strongly modulated by the boreal summer intraseasonal oscillation (BSISO). BSISO, with a prominent northward propagation feature over the Western North Pacific (WNP) as well as in the Indian Ocean (IO), is the primary source of short-term climate variability and predictability in the Asian summer monsoon region. This talk overviews our recent studies on the role of air-sea interaction on propagation, variability, and predictability of BSISO. Firstly, air-sea interaction plays a dominant role in the BSISO propagation over the WNP, whereas the mean vertical wind shear mechanism is the major driver over the IO. The meridional gradient of mean sea surface temperature and moisture over the WNP provides a favorable condition for northward propagation of BSISO convective activities by promoting upward transport of heat and moisture from surface to lower troposphere. Secondly, contributed by dynamical and air-sea interaction processes, the BSISO-related convections are stronger and more organized with northward propagation on 30-60-day timescales during El Niño developing (E-DV) than decaying (E-DC) summers over the WNP. The air-sea interaction in E-DV gets stronger due to the larger meridional gradient of sea surface temperature, amplifying northward propagation of BSISO than in E-DC. Lastly, climate models’ capability in representing multiscale interactions contributed by air-sea interaction is crucial for improving the subseasonal prediction skill of BSISO and the associated extreme precipitation events.
