Sensitivity of a tropical-temperate trough to sea-surface temperature anomalies in the Agulhas retroflection region

Abstract

The Colorado State University Regional Atmospheric Modelling System’s (RAMS) sensitivity to positive variations in sea-surface temperature is tested by adding positive anomalous temperatures to the ocean surface in the region of the Agulhas Current retroflection for a simulated period of four days from 21 to 24 January 1981. The simulated circulation and precipitation values of the sensitivity test are compared with a control simulation. The results of the experiment, although limited in response did result in noticeable increases in convective precipitation and are consistent with the expected climate responses to anomalously high seasurface temperatures in this area. These simulated circulation changes are consistent with previously hypothesised features of ocean-atmosphere interaction for the Agulhas Current region. The development of the ocean anomaly served to intensify the seasurface temperature front, leading to a poleward shift in the near-surface westerlies.

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