Effects of tropical sea surface temperature (SST) errors on the Antarctic atmospheric circulation of HadCM3

This paper investigate the large mean sea level pressure errors in the HadCM3 atmosphere-ocean global climate model around Antarctica and finds them to be caused by the sea surface temperature (SST) errors in the winter tropics. This teleconnection is explained by the warm tropical SST anomalies causing anomalous ascent which strengthens the Hadley circulation and increases the high-level (∼200hPa) divergence. This in turn interacts with the strong meridional gradient in absolute vorticity to generate Rossby waves that propagate polewards. By imposing SST anomalies, in the atmosphere only model, in different ocean basins it is shown that it is the SST errors over Indonesia and the eastern tropical Atlantic that are responsible for these wave trains; and hence, primarily responsible for the pressure anomalies. By contrast, a large SST error over the eastern tropical Pacific does not cause a wave train to be generated because it does not generate strong ascent. This study also demonstrates the difficulties in diagnosing errors within a coupled climate model since forcing, particularly in the tropics, may have a strongly non-local effect.

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