Implied Ocean Heat Transports in Recent AGCM Simulations: Sensitivity to the Surface Energy Budget

Peter Gleckler and Karl Taylor Program for Climate Model Diagnosis and Intercomparison Lawrence Livermore National Laboratory gleckler1@llnl.gov

The oceanic meridional energy transport (OMET), implied by the annual mean net surface heat flux, helps to evaluate an AGCM's readiness for coupling with an ocean GCM. Here we revisit the sensitivity of OMET to the dominant terms of the surface energy budget in models participating in the Atmospheric Model Intercomparison Project (AMIP). Gleckler et al. (1995, GRL, 22, 791-794) demonstrated that OMET implied by AGCMs is critically sensitive to cloud radiative effects. Excessive shortwave cloud forcing led to insufficient surface heating in the low latitudes in many models, resulting in wildly different profiles of OMET in the Southern Hemisphere. The implication was that improvements in the modeled cloud-radiative effects would yield at least some southward ocean heat transport in the Southern Hemisphere (OMET implied by most models was northward at all latitudes). More recently, Hack (1998, J. Climate, 11, 1237-1244) demonstrated that the OMET implied in CCM3 was at least as sensitive to the latent heat flux and attributable to the choice of the deep convection scheme. Using a collection of recent AMIP simulations, in this presentation we examine the relative OMET sensitivity to the dominant terms of the surface energy balance.