The Influence of Sea Surface Temperature Gradients on Stratiform Cloudiness along the Equatorial Front in the Pacific Ocean

Abstract

Satellite observations of visible cloudiness and sea surface temperature (SST) are used to test the hypothesis that the configuration of cool low-level winds blowing across a sharp SST front in the equatorial eastern Pacific gives rise to stratiform clouds on the warm (downstream) side of the front. The results show that there is a maximum in low clouds over the equatorial front during the cold season of 1988 when the front and cross-isotherm winds were strong. The low-cloud maximum was reduced in the warm El Niño year of 1987, consistent with the weakening of the front. Instability waves along the equatorial front were pronounced during the summer and autumn of 1988. The results show a strong association between visible cloud and the SST waves, with enhanced (reduced) cloudiness in the warm troughs (cold crests) of the waves.