Date of Award
Doctor of Philosophy (PhD)
Atmospheric & Oceanic Sciences
An ocean general circulation model (the Hybrid Coordinate Ocean Model, HYCOM) is used to examine the impact of atmospheric intraseasonal oscillations (ISOs) on intraseasonal sea surface temperature (SST) during boreal summer, and on seasonal to interannual SST, mixed layer thickness (hm) and upper ocean heat content (uoheat) in the Indian Ocean (IO). In evaluating the intraseasonal SST impacts of atmospheric ISOs, the effects of the Madden- Julian Oscillation (MJO; 30-90 days) and submonthly ISOs are separately examined. The maximum summertime SST variability occurs in the Arabian Sea, the Bay of Bengal, and the eastern equatorial IO. Intraseasonal wind has a much larger impact on intraseasonal SSTs than either shortwave radiation or precipitation. Surface turbulent heat fluxes (THF) and entrainment due to changing intraseasonal wind speeds have a larger impact on SSTs than upwelling or horizontal advection due to changing intraseasonal wind stress in the Arabian Sea and in the Bay of Bengal, while the impacts of wind speed and wind stress are relatively equal in the eastern equatorial IO. Existing studies have shown that ISOs rectify onto low-frequency equatorial surface currents and cross-equatorial transport, suggesting that they may also have important impacts on lowfrequency upper ocean variability. Results indicate that rectification of ISOs onto seasonal and interannual upper ocean variability can be significant, and that it is highly regional. The regions displaying maximum rectification vary between SST, hm, and uoheat, and between seasonal and interannual timescales. Intraseasonal wind speed and wind stress have a much larger impact on seasonal and interannual SST, hm, and uoheat than either intraseasonal shortwave radiation or precipitation. The relative importance of entrainment and THF due to intraseasonal wind speed, and of upwelling and horizontal advection due to intraseasonal wind stress, varies by region.
Duncan, Benet Elizabeth, "Impact of Atmospheric Intraseasonal Oscillations on Multi-Timescale Variability in the Upper Indian Ocean" (2011). Atmospheric & Oceanic Sciences Graduate Theses & Dissertations. 11.