Marine boundary layer modification across the edge of the Agulhas Current


  • Mark Jury,

  • Nan Walker


Aerial survey results are presented which show a modification of the lower atmosphere on crossing the edge of the Agulhas Current near 37°S, 20°E. Profiles of air temperature and dewpoint show increases in marine boundary layer heights of about 400 m as sea surface temperatures rise suddenly from 18° to 24°C. Westerly winds increase across the NE-SW aligned sea surface temperature front by 7 m s−1, in a sea breeze-like circulation. Surface latent and sensible heat fluxes to the atmosphere change from 100 W m−2 to 340 W m−2 on entering the Agulhas Current because of feedback processes between warmer sea surface temperatures, turbulence, and wind stress. The data sample is small and statistically limited, but the case study results indicate that the response of the lower atmosphere to the Agulhas Current is similar to that found over the Gulf Stream and other warm western boundary currents.