Covariability of SST and surface heat fluxes in reanalyses and CMIP3 climate models

The generation and dissipation of SST anomalies is mediated by the covariability of SST and surface heat fluxes. The heat fluxes, including the net flux and its radiative and turbulent components, and their connection to SST are investigated in the NCEP-NCAR and ERA-40 reanalyses and in the CMIP3 multi-model collection of climate simulations. The covariance patterns between SST and heat fluxes are similar from the two reanalyses. The upward heat fluxes are correlated with the SST anomalies in the tropical central-eastern Pacific and at northern Pacific and Atlantic mid-latitudes. The negative covariance between temperature and heat flux in the tropical central-eastern Pacific is seen in all the climate models in addition to the ensemble mean. However, the covariance at mid-latitudes varies considerably among the models. Lagged covariances, on the other hand, are broadly similar in the two reanalyses and among models, suggesting that heat flux feedback is comparable. Heat flux feedback is determined from the lagged cross-covariances together with the auto-covariance of SST. It is negative and is dominated by the turbulent component. Strongest feedback is found at mid-latitudes in both hemispheres, with largest values occurring in the western and central portions of the oceans with extensions to higher latitudes. The latter are also areas with high inter-model variation.