Characteristics of Rossby Waves in the Indian Ocean

Long wavelength baroclinic oceanic Rossby waves are of interest because they are the main mechanism of energy transfer among the oceanic basins as the rotating fluid adjusts under the forcing of gravity and buoyancy.They play an important role in dynamics and thermodynamics in the ocean.The signature of them is evident from the altimeter measurements.Sea surface height derived from the multiple ocean satellite altimeter missions over 1993～2008 is analyzed to systematically investigate the characteristics of the Rossby waves in the tropical Indian Ocean,by jointly adopting 2D-FFT,2D-Radon Transform,Complex Empirical Orthogonal Function and the classic linear theory methods.Results are as follows.The energy of Rossby wave is mainly concentrated between 5°S～18°S.Annual Rossby wave can be observed all over the whole basin, whereas semi-annual Rossby wave can be only detected in the equatorial area,and inter-annual Rossby wave in the off-equatorial region.The phase speeds of Rossby waves detected from altimeter satellites are basically in agreement with the calculation based on the classic linear theory, but the former are some slower(faster) north(south) of 15°S than the later.Furthermore,it is indicated from the CEOF analysis that the annual Rossby wave is apparent in the Bay of Bengal, Arabian Sea and the open south Indian Ocean,whereas inter-annual Rossby wave mainly presents in the south Indian Ocean,and eastward Kelvin wave is dominant along the equator.