| Summary: | The performance of 20 models from the Atmospheric Model Intercomparison Project (AMIP) was evaluated concerning surface radiation over the tropical oceans (30° S−30° N) from 1979 to 2000. The model ensemble mean of the net surface shortwave radiation (<i>Q<sub>SW</sub></i>) was underestimated compared to the International Satellite Cloud Climatology Project (ISCCP) data by 4 W m<sup>−2</sup>. On the other hand, net longwave radiation (<i>Q<sub>LW</sub></i>) was overestimated by 4 W m<sup>−2</sup>, leading to an underestimation of the net surface radiation (<i>Q<sub>rad</sub></i>) by 8 W m<sup>−2</sup>. The most prominent bias in the <i>Q<sub>rad</sub></i> appears to be over regions of low-level clouds in the off-equatorial eastern Pacific, eastern Atlantic, and the south-eastern Indian Ocean. The root means squared error of <i>Q<sub>LW</sub></i> was larger than that of <i>Q<sub>SW</sub></i> in 17 out of 20 AMIP models. Overestimation of the total cloud cover and atmospheric humidity contributed to the underestimation of <i>Q<sub>rad</sub></i>. In general, models with higher horizontal resolutions performed slightly better than those with coarser horizontal resolutions, although some systematic bias persists in all models and in all seasons, in particular, in regions of low-level clouds for <i>Q<sub>LW</sub></i><sub>,</sub> and high-level clouds for <i>Q<sub>SW</sub></i><sub>.</sub> The ensemble mean performed better than most models, but two high-resolution models (GFDL-HIRAM-C180 and GFDL-HIRAM-C360) outperform the model ensemble.
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