HR: 1300h
AN: OS52D-09    [PDF]
TI: The Effects of the Seasonal Cycle on Interannual Variability of SST in the Tropical Indian Ocean
AU: * Halkides, D J
EM: halkides@monsoon.colorado.edu
AF: Program in Atmospheric and Oceanic Sciences (PAOS), University of Colorado STAD 255, Gate 7, 311 UCB, Boulder, CO 80303 United States
AU: Han, W
EM: whan@monsoon.colorado.edu
AF: Program in Atmospheric and Oceanic Sciences (PAOS), University of Colorado STAD 255, Gate 7, 311 UCB, Boulder, CO 80303 United States
AB: Modulation of sea surface temperature (SST) patterns by interactions between seasonal and interannual variabilities in the Indian Ocean (IO) region are studied via a hierarchy of experiments utilizing a 4-1/2 layer ocean model in a realistic tropical Indian Ocean basin. Results demonstrate that seasonal atmospheric forcing amplifies positive (negative) temperature anomalies in the western (eastern) IO basin associated with Indian Ocean Zonal Mode (IOZM) events. In particular, when seasonal variability is removed from the atmospheric forcings, both the 1994 and 1997 IOZM events show decreases in the magnitude of interannual SSTa on the order of $1^{\circ}$C, respective to a control run, in both IOZM antinode regions during October-November. Similar results occur for these same events when the seasonal scale forcings are not removed, but shifted in time by n=\{3, 6, 9\} months with respect to the interannual anomalies in the forcing fields. These results are qualitatively similar to those found by others regarding interactions between the El Nino-Southern Oscillation and seasonal variability in the Pacific Ocean. Additionally, our work for the IO region shows that when seasonal scale forcing is removed from the system, the 1994 cool event in the eastern basin is prolonged by approximately two months, and eastern temperature anomalies succeeding the 1997/98 cool event are slow to warm-up in comparison to eastern SSTa in the control solution. This indicates the seasonal cycle is at least partly responsible for the timely termination of IOZM events at the end of an event year. Work is currently in progress to examine the physical processes leading to SST modulation by seasonal variability in the IO. This work involves a partial coupling of the 4-1/2 layer ocean to an atmospheric mixed layer model, forced by a combination of observed Florida State University (FSU) winds and SST generated by the ocean model. Heat fluxes generated by the model atmosphere are used in turn to help force the ocean.
DE: 1620 Climate dynamics (3309)
DE: 4215 Climate and interannual variability (3309)
DE: 4231 Equatorial oceanography
DE: 4522 El Ni¤o
DE: 4599 General or miscellaneous
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting