Abstract ID: 260
Boreal Summer Intraseasonal Oscillation: Propagation, Interannual Variability, and Impacts on Extremes
Lead Author: June-Yi Lee
Research Center for Climate Sciences, Pusan National University, Republic of Korea
Keywords: Boreal Summer Intraseasonal Oscillation, Air-Sea Interaction, Northward Propagation, El Niño, subseasonal prediction and predictability
Abstract: Extreme weather and climate events such as torrential rainfalls and heat waves over Asia and Europe during boreal summer 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 recent scientific advances in understanding mechanism of propagation, interannual variability, and impacts of BSISO. Firstly, recent studies suggest that 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, BSISO strongly modulates extremes including heat waves, extreme precipitation, and tropical cyclones over Asia and Europe. It is suggested that climate models’ capability in representing BSISO is crucial for improving the subseasonal prediction skill of BSISO and the associated extreme precipitation and heat wave events.
Co-authors:
Young-Min Yang, Key Laboratory of Meteorological Disaster, Nanjing University of Information Science and Technology, Nanjing, China
Doo-Young Lee, Research Center for Climate Sciences, Pusan National University, Busan, Republic of Korea
Pang-Chi Hsu, Key Laboratory of Meteorological Disaster, Nanjing University of Information Science and Technology, Nanjing, China
