Bias of atmospheric shortwave absorption in the NCAR Community Climate Models 2 and 3: Comparison with monthly ERBE/GEBA measurements

Abstract

A direct comparison is made of collocated shortwave reflection at the top of the atmosphere and insolation at the surface between the National Center for Atmospheric Research Community Climate Models 2 and 3 (CCM2 and CCM3) and monthly Earth Radiation Budget Experiment/Global Energy Balance Archive (ERBE/GEBA) measurements. It is shown that atmospheres in the models are brighter at the top of the atmosphere than ERBE measurements and meanwhile transmit more solar radiation to the surface than GEBA measurements. As a consequence, the models underestimate atmospheric shortwave absorption. The amount of this underestimation is about 20 W m−2 in CCM2 and 17 W m−2 in CCM3. It is emphasized that regardless of whether the bias is in clear sky or in clouds, this underestimation has important implications for the intensity of the hydrological cycle and thus circulation in the models.