Monday, 7 July 2014
In Part I of this study (Stanfield et al. 2014), the NASA GISS CMIP5 (C5) and Post-CMIP5 (P5) simulated cloud properties were assessed utilizing multiple satellite observations, with a particular focus on the southern mid-latitudes (SMLs). This study applies the knowledge gained from Part I of this series to evaluate the modeled TOA radiation budgets and cloud radiative effects (CREs) using CERES EBAF (CE) satellite observations. Comparisons have revealed that the P5 and C5-simulated global patterns of clear-sky and all-sky outgoing longwave radiation (OLR) match well with CE observations, with negative biases in both P5 and C5-simulated clear-sky OLR. Global clear-sky and all-sky albedos have minimal differences overall between the model simulations, however, P5-simulated all-sky albedo has slightly increased over the SMLs due to the increase in low-level CF from the new planetary boundary layer (PBL) scheme. Clouds are shown to have a warming effect of 26.2 W m-2 on the TOA longwave (LW) radiation budget, but a strong cooling effect of -47.2 W m-2 on the TOA shortwave (SW) radiation budget, resulting in a net cooling effect of -21 W m-2 on the TOA radiation budget. Our sensitivity study has illustrated that the cooling effect of SW CRE increases with CF at a magnitude of ~1.1 W m-2 %-1 and a correlation of ~0.9. The modeled sensitivities and correlations of SW CRE to CF are fairly close to the observation over the tropics, but much lower over the mid-latitudes. Large improvements, however, are noted over the mid-latitudes in the P5 simulation. Comparing our results with the cloud property comparisons presented in Part I, the modeled TOA radiation budgets and CREs agree well with the CE observation, with higher correlations and smaller standard deviations. These results, combined with the results in the Part I, have quantitatively estimated how much improvement is found in the P5-simulated cloud and radiative properties, particularly over the SMLs and tropics, due to the implementation of the new PBL and convection schemes.
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