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Underestimation of Latent and Sensible Heat Fluxes above the Agulhas Current in NCEP and ECMWF Analyses

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  • 1 Ocean Climatology Research Group, Department of Oceanography, University of Cape Town, Rondebosch, Cape Town, South Africa
  • | 2 ECMWF, Reading, Berkshire, United Kingdom
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Abstract

The Agulhas Current is the major western boundary current of the Southern Hemisphere. South of Africa it retroflects back into the southwest Indian Ocean, transporting relatively warm water into the midlatitudes. Large sensible and latent heat transfers from the Agulhas Current and its retroflection to the atmosphere occur throughout the year, but particularly during winter. This study suggests that the NCEP and ECMWF models tend to underestimate these fluxes because they are unable to adequately represent the air–sea fluxes over the warmest waters in the core of the current. This core is only 80–100 km wide and it is suggested that the SST data used by these models do not have fine enough spatial resolution to properly represent the Agulhas Current and its mesoscale variability.

Corresponding author address: Dr. C. J. C. Reason, EGS Dept. and Dept. of Oceanography, University of Cape Town, Private Bag, 7701 Rondebosch, Cape Town, South Africa. Email: cjr@egs.uct.ac.za

Abstract

The Agulhas Current is the major western boundary current of the Southern Hemisphere. South of Africa it retroflects back into the southwest Indian Ocean, transporting relatively warm water into the midlatitudes. Large sensible and latent heat transfers from the Agulhas Current and its retroflection to the atmosphere occur throughout the year, but particularly during winter. This study suggests that the NCEP and ECMWF models tend to underestimate these fluxes because they are unable to adequately represent the air–sea fluxes over the warmest waters in the core of the current. This core is only 80–100 km wide and it is suggested that the SST data used by these models do not have fine enough spatial resolution to properly represent the Agulhas Current and its mesoscale variability.

Corresponding author address: Dr. C. J. C. Reason, EGS Dept. and Dept. of Oceanography, University of Cape Town, Private Bag, 7701 Rondebosch, Cape Town, South Africa. Email: cjr@egs.uct.ac.za

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