The response of convection to changing sea surface temperature (SST) in the absence of large scale flow is examined, using a three dimensional cloud resolving model. The model includes a 5 category bulk microphysical scheme representing snow, ice, graupel, rain and cloud amounts in addition to an interactive radiation scheme for the shortwave and infrared. Long integrations are made to achieve a radiative-convective equilibrium state for a range of SSTs, for which cloud and convection statistics are analysed.
The main conclusion is that, despite significant temperature sensitivities in many of the conversion terms between bulk water categories, convection is very insensitive to changing SST in the absence of large-scale flow. This is a result of the moist adiabatic temperature profile that the tropical atmosphere is constrained to take. A parcel of air rising through a deep convective cloud experiences approximately the same range of temperatures, but at higher altitudes as SST increases. Thus the vertical profiles of cloud fraction and other cloud related statistics are simply shifted in height, but not changed in overall magnitude. This result agrees with observational studies of the sensitivity of convection to SST.