83rd Annual

Tuesday, 11 February 2003: 4:45 PM
Role of the Indian Ocean SST anomalies in the coupling of the Atmosphere and Ocean
C. Perigaud, California Institute of Technology/JPL, Pasadena, CA; and D. J. Neelin and J. McCreary
Poster PDF (31.0 kB)
Observed SST variations over 1980-2000 are used to force a quasi-equilibrium tropical atmosphere model in 2 experiments. In Experiment 1, variations are considered over the three tropical oceans. In Experiment 0, variations are considered over the Pacific and Atlantic oceans, but not over the Indian Ocean where the SST variations are prescribed to their climatological values. Whereas in both experiments, the model is reasonably successful in simulating the atmospheric anomalies in the central and eastern Pacific, only Experiment 1 is successful in simulating the two major Indian Ocean events of this period, with the two major rainfall deficits in 1994 and 1997 over the South Eastern Indian ocean (SEIO).

Then, a four-active-thermodynamic-layer-model of the Indian Ocean is used to analyze the importance of the rainfall-salinity variations for this ocean. The ocean model is forced by the climatological rainfalls to which we add the anomalies simulated by Experiment 1 or Experiment 0. As expected, the Sea Surface Salinity (SSS) simulated in the SEIO is saltier for Experiment 1 than for Experiment 0. The interesting result is that the SST is also significantly affected. It is affected on the east side of the equator offshore

of Java. While Experiment 0 simulates an anomaly smaller than 0.5C, Experiment 1 simulates two cold anomalies of 2C, in much better agreement with the observed SSTs. These experiments demonstrate the important role of the Indian Ocean SST anomalies in the ocean-atmosphere coupled processes for this ocean where salinity variations cannot be neglected.

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