The Rossby wave as a key mechanism of Indian Ocean climate variability

We analyze the time-longitude structure of composite cases from model-assimilated ocean data in the period 1958-1998, following on from earlier work by Huang and Kinter (J. Geophys. Res. 107(Cl 1) (2002) 3199) that studied east-west thermocline variability in the Indian Ocean. Our analysis focuses on the Rossby wave signal along the thermocline ridge in the tropical SW Indian Ocean (10degreesS, 60-80degreesE), where wind stress curl is important. Anomalous winds in the equatorial east Indian Ocean force successive Rossby waves westward at speeds of 0.1 m s(-1) +/- 30%. With a wavelength of similar to7000 km, the period of oscillation is in the range 1.9-5.2 years. The Indian Ocean Rossby wave is partially resonant with the global influence of the Ell Nino-Southern Oscillation, except during quasi-biennial rhythm. The presence of the Rossby wave offers potential predictability for east-west atmospheric circulation systems and climate that affect resources in countries surrounding the Indian Ocean. (C) 2004 Elsevier Ltd. All rights reserved.