Upwelling physics off West Africa : evidences of seasonal cooling caused by dry air mass intrusions against warming upwelling

An oceanographic and meteorological buoy, dedicated to monitoring and analysis of the natural variability and anthropogenic change of the Senegalese coastal upwelling, was deployed early 2015. We present a closed heat budget analysis of the sea surface temperature variations, over 2016-2017, year of an exceptional ENSO. Our observational study evidences paradoxical results regarding the cooling processes during part of the six-month upwelling season. Latent heat loss by intrusions of dry air seasonally takes over the wind-stress driven upwelling dynamics. The latter instead even warms the surface due to intrusion of subsurface waters with temperature inversions. Results are supported by a numerical study, and challenge our canonical conception of coastal upwelling functioning.