Interaction between Net Shortwave Flux and Sea Surface Temperature

Abstract

Ocean surface shortwave irradiance estimates, From GOES satellite data computed using the model of Gautier and Frouin (1985), are compared to in situ measurements from research vessels and buoys during the frontal air-sea interaction experiment (FASINEX). They reveal that the satellite method overestimates percentage cloudiness during fractional cloud cover and large satellite viewing angles. An empirical relationship, based on physical constraints, is developed to correct for the overestimation of percentage cloud cover under these conditions. Subsequent comparisons of the corrected satellite estimates with in situ measurements show a root-mean-square difference of 10% of the daily mean values, with a mean difference between satellite and in situ data of 1?10 W m?2. From fields of corrected satellite estimates a cloudiness parameter, called the equivalent cloud amount, is used to examine the influences and feedbacks between the clouds and the sea surface temperatures (SST's). Correlations between cloud and SST fields show a high day-to-day variability attributed to the passage of several large-scale frontal cloud bands. The monthly mean correlation, however, shows large, positive values. This indicates that in the mean there are more clouds and/or clouds with higher liquid water content over the colder northern waters versus the warmer southern waters. Thus, the longer-term mean cloudiness field may act in a positive feedback sense, keeping the cold water from gaining as much heat as the already warmer water.