Understanding the Equatorial Pacific Cold Tongue Time-Mean Heat Budget. Part II: Evaluation of the GFDL-FLOR Coupled GCM

AbstractThe heat budget of the Pacific equatorial cold tongue (ECT) is explored using the GFDL- FLORcoupled GCM (the forecast-oriented low ocean resolution version of CM2.5) and ocean reanalyses, leveraging the two-layer framework developed in Part I. Despite FLOR’s relatively weak meridional stirring by tropical instability waves(TIWs), the model maintains a reasonable SST and thermoclinedepth in the ECT via two compensating biases: 1) enhanced monthly-scale vertical advectivecooling below the surface mixed layer (SML), due to overly cyclonic off-equatorial wind stressthat acts to cool the equatorial source waters; and 2) an excessive SST contrast between the ECT and off-equator areas, which boosts the equatorward heat transport by TIWs. FLOR’s strong advectivecooling at the SML base is compensated by strong downward diffusion of heat out of the SML, which then allows FLOR’s ECT to take up a realistic heat flux from the atmosphere. CorrectingFLOR’s climatological SST and wind stressbiases via flux...