The climatic importance of atmospheric IntraSeasonal Oscillations (ISOs) in the tropical Indian Ocean has been receiving increasing attention. Reflecting this importance, extensive modeling studies, together with a few newly deployed mooring observations, have significantly advanced our understanding of various aspects of Indian Ocean variability induced by atmospheric ISOs in the past a few years. This understanding, however, is far from complete and many outstanding science issues remain unaddressed.
The objectives of the proposed project are to explore: (i) How and why do the surface and subsurface meridional currents in the equatorial Indian Ocean respond to atmospheric ISOs (especially the dominant 30-60 day and quasi-biweekly oscillations), and how does that response impact multi-timescale variability of cross-equatorial heat transport? (ii) What are the seasonality and interannual variability of the upper Indian Ocean response to atmospheric ISOs? (iii) How do atmospheric ISOs affect the variability of tropical Indian Ocean (especially the warm pool) heat content?
The primary tool for this project is an ocean general circulation model. Satellite data combined with daily reanalysis from the European Center for Medium range Weather Forecasts will be used as the model forcing fields. The realistic representation of physics in the ocean model allows for a direct investigation of how the ocean responds to the intraseasonal atmospheric forcing. To provide insights into the key oceanic processes involved, a linear continuously stratified model and a nonlinear intermediate ocean model will also be used. Available data in the Indian Ocean will be analyzed, compared with, and interpreted by the model solutions. The proposed research is scientifically important because interannual variability of the tropical Indian Ocean (the part that is independent of ENSO) is not well understood, and the cross-timescale impact of atmospheric ISOs has been suggested. The project addresses a central theme of climate research and is essential for understanding the role of atmospheric ISOs in causing multi-scale climate variability in the tropics. The intellectual merit of the proposed project lies in its contribution to advancing our understanding of, and providing new insight into, how and why the tropical Indian Ocean responds to intraseasonal atmospheric forcing, a study that will build a solid foundation for identifying the role played by atmospheric ISOs in causing climate variability in the tropical coupled ocean/atmosphere system. By integrating the research with education, the project will have a broader impact on our society through both advancing climate research and promoting graduate education.
