National Aeronautics and Space Administration

Abstract:
In this talk I will explore two different perspectives of the role of marine surface sensible and latent heat fluxes in the climate system. One perspective holds that the role of ocean surface fluxes is to balance the global atmospheric energy loss by infrared emissions to space that is regulated by the horizontal and vertical organization of cloudiness. An alternative perspective considers the role of surface fluxes in regulating cloud organization that in turn affects infrared emissions to space as well as patterns of ocean heating and cooling. Climate and forecast models use a variety of algorithms to estimate marine surface fluxes which can impact model cloudiness and cloud system variability. I illustrate these differences by applying a simple set of surface flux diagnostics to a suite of CMIP6 simulations, and apply an offline surface flux “correction” to simulated fluxes to estimate their biases relative to the Fairall et al. (1996; 2003) state-of-the-art COARE3.6 bulk flux algorithm. These corrections suggest a sensitivity to choice of flux algorithm of several modes of tropical rainfall, including the mean position of the intertropical convergence zone (ITCZ) and the Madden-Julian oscillation (MJO). Subsequent tests with the NCAR CESM2 confirm these sensitivities, and suggest that revising model surface flux algorithms to conform with those estimated with the COARE3.6 algorithm may reduce model biases in tropical rainfall. I conclude with a summary of ongoing efforts to update the CESM2 flux algorithm to include additional corrections for the ocean cool skin and diurnal warm layer as well as the effects of freshwater lenses, which appear to play an under-appreciated role in regulating the MJO lifecycle.