Long-term behavior of cloud systems in TOGA COARE and their interactions with radiative and surface processes. Part III: Effects on the energy budgetand SST

Most atmospheric general circulation models (GCMs) and coupled atmosphere-o cean GCMs are unable to get the tropical energy budgets at the top of the a tmosphere and the surface to simultaneously agree with observations. This a spect is investigated using a cloud-resolving model (CRM) that treats cloud -scale dynamics explicitly, a single-column model (SCM) of the National Cen ter for Atmospheric Research (NCAR) Community Climate Model that parameteri zes convection and clouds, and observations made during Tropical Oceans and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE ). The same large-scale forcing and radiation parameterizations were used i n both modeling approaches. We showed that the time-averaged top-of-atmosph ere and surface energy budgets agree simultaneously with observations in a 30-day (5 December 1992-3 January 1993) cloud-resolving simulation of tropi cal cloud systems. The 30-day time-averaged energy budgets obtained from th e CRM are within the observational accuracy of 10 W m(-2), while the corres ponding quantities derived from the SCM have large biases. The physical exp lanation for this difference is that the CRM realization explicitly represe nts cumulus convection, including its mesoscale organization, and produces vertical and horizontal distributions of cloud condensate (ice and liquid w ater) that interact much more realistically with radiation than do paramete rized clouds in the SCM. The accuracy of the CRM-derived surface fluxes is also tested by using the fluxes to force a one-dimensional (1D) ocean model. The 1D model, together with the surface forcing from the CRM and the prescribed advection of tempe rature and salinity, simulates the long-term evolution and diurnal variatio n of the sea surface temperature. This suggests that the atmosphere-ocean c oupling requires accurate representation of cloud-scale and mesoscale proce sses.