Influence of western boundary reflection on seasonal circulation in the equatorial Indian Ocean

Abstract

The influence of western boundary reflection (WBR) of Rossby waves on the seasonal circulation in the equatorial Indian Ocean is investigated using an ocean model LICOM , forced by daily winds and surface fluxes of the National Centers for Environmental Prediction (NCEP) reanalysis I during 2000–2010. LICOM has reproduced seasonal variations of Ocean Surface Current Analysis Real-time (OSCAR) zonal currents and satellite altimeter sea level well. Comparisons of the experimental results with and without WBR suggest that the WBR enhances the zonal currents and sea level variations in the central and eastern equatorial Indian Ocean. Long equatorial wave dynamics analyses suggest that the difference of the second baroclinic mode waves with and without WBR are evidently larger than those of the first baroclinic mode, suggesting the importance of the second baroclinic mode waves in controlling the sea level and zonal current seasonal variations. Analyses also suggest that reflected Kelvin waves from the first and second baroclinic modes have a much larger contribution to the semiannual oscillations of the sea level than Rossby waves. The first meridional Rossby wave of the first and second baroclinic modes have larger contribution to zonal currents than the Kelvin waves from the WBR. These results suggest the important role of the WBR in controlling the seasonal circulation in the equatorial Indian Ocean.