Abstract

An idealized energy-balance model for a closed circulation is first presented to illustrate the coupling between the net tropospheric radiative cooling, the surface fluxes and the mean subsidence away from the precipitation zones. Then a one-dimensional diagnostic model and a radiation model with boundary layer clouds are combined to explore this coupling for a specific region using mean sounding data over the tropical Pacific. The radiatively driven subsidence rate at the top of the convective boundary layer is approximately 35 mb day−1 (0.04 Pa s−1 and is largely independent of boundary layer cloud fraction. The sensitivity of the corresponding convective heat flux profiles to the mass divergence profile and cloud fraction within the boundary layer is explored. Reasonable assumptions give realistic surface sensible and latent heat fluxes for this region of approximately 10 and 130 W m−1. The paper illustrates the important background climatic control of the radiation field on the tropical surface fluxes.

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