The Role of Mesoscale Sea-Surface Temperature Variability in Organizing Tropical Convection

Sea-surface temperature (SST) variability in the tropical warm pool regions is typically no more than 2-3 degrees over distances of 100's of km. An important question concerns the role that SST variations have in the initiation and subsequent organization of deep convection. Simulations are presented that examine the effects of warm SST anomalies on convective formation under a range of SST values and differing wind speeds over a domain of roughly 1000 x 500 km using a cloud resolving large-eddy simulation model. Results suggest that warm patch anomalies of ~1.5 degrees over a ~200 km scale region will both concentrate the formation of convection and promote long-lived convective clusters that strongly modify the surface winds and fluxes, depending on the background wind speed. For background winds of 12 m/s, convection is focused downwind from the warm patch and persists for 4 days or longer. Wind speeds under the convective cluster are lower than surrounding winds, whereas winds over the warm patch are slightly higher. Increased winds over the warm patch can be attributed to enhanced boundary layer mixing, whereas the decrease in winds under the cluster result from convective cold pools. Imposing a stronger background wind of 18 m/s disrupts the convective organization, reducing the influence of the SST warm patch. Analysis of scatterometry and satellite SST data are planned to verify if these effects can be measured.