Convection in the east Pacific Intertropical Convergence Zone

Abstract

The eastern tropical Pacific exhibits a strong, cross-equatorial sea surface temperature (SST) gradient, which drives a southerly flow in the atmospheric boundary layer. Convergence in this flow is generally considered to drive deep convection in the east Pacific Intertropical Convergence Zone. However, results from cloud modeling and recent field programs provide an alternative thermodynamic mechanism for controlling this convection. While shallow convection responds to boundary layer convergence, deep convection appears to be controlled by a combination of convective inhibition, surface moist entropy fluxes, tropospheric relative humidity, and moist convective instability. These factors explain the sharp minimum in infrared brightness temperature near 8°N while boundary layer convergence occurs over a much broader range of latitudes.