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Intraseasonal sea surface warming in the western Indian Ocean by oceanic equatorial Rossby waves

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OSTP Journal Article

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Naval Research Laboratory Stennis Space Center United States

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A novel process is identified whereby equatorial Rossby ER waves maintain warm sea surfacetemperature SST anomalies against cooling by processes related to atmospheric convection in the western Indian Ocean. As downwelling ER waves enter the western Indian Ocean, SST anomalies of 0.15C developnear 60E. These SST anomalies are hypothesized to stimulate convective onset of the Madden-JulianOscillation. The upper ocean warming that manifests in response to downwelling ER waves is examined in amixed layer heat budget using observational and reanalysis products, respectively. In the heat budget,horizontal advection is the leading contributor to warming, in part due to an equatorial westward jet of 80 cm s1 associated with downwelling ER waves. When anomalous currents associated with ER waves areremoved in the budget, the warm intraseasonal temperature anomaly in the western Indian Ocean iseliminated in observations and reduced by 55 in reanalysis.

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  • Physical and Dynamic Oceanography

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