Effects of zonal perturbations of sea surface temperature on tropical equilibrium states: A cloud-resolving modeling study

The effects of zonal perturbations of sea surface temperature (SST) on tropical equilibrium states are investigated based on a series of two-dimensional cloud-resolving simulations with imposed zero vertical velocity, constant zonal wind, and a zonal model domain of 768 km. Four experiments with zonal SST perturbations of wavenumbers 1 (Cl), 2 (C2), 4 (C3), and 8 (C4) are compared to a control experiment with zonally uniform SST (CO). The 40-day integrations show that the temperatures reach quasi-equilibrium states with distinct differences. Cl and C2 produce warmer equilibrium states whereas C3 and C4 generate colder equilibrium states than CO does. The heat budgets in the five experiments are analyzed. Compared to CO, less IR cooling over smaller clear-sky regions in Cl and more condensational heating in C2 are responsible for wanner equilibrium states. A reduced condensational heating leads to the cold equilibrium state in C3. The interaction between convective systems in C4 causes a decrease of condensational heating, which accounts for the cold equilibrium state.