Influence of Sea Surface Temperature on the Columnar Water Vapor Content and Cloud Fraction, Based on Monthly-Averaged MODIS Data at 1° by 1° Resolution

Abstract. Satellite data on global sea surface temperature (SST), water vapor and cloud fraction are analyzed to provide direct relationships on these parameters. Increase in SST elevates the water vapor pressure at the surface following the Clausius-Clayperon (exponential) form, and this effect persists to increase the columnar water vapor up to SST of approximately 300 K, at the 1° by 1°, monthly-averaged scale. Beyond SST of 300 K, a steeper slope for the columnar water vapor is observed. A similar transitional relationship is observed between cloud fraction (CF) and SST, except that a negative slope is found up to SST of 300 K. Then, a reversal occurs at SST of approximately 300 K where CF increases quadratically as a function of SST. Parameterization of water vapor and CF is provided as a function of SST for 1° by 1° spatial resolution and monthly-averaged time scale.