Evaluation of Clouds in Version 1 of the E3SM Atmosphere Model With Satellite Simulators

Abstract

This study systematically evaluates clouds simulated by the Energy Exascale Earth System Model Atmosphere Model version 1 (EAMv1) against satellite cloud observations. Both low- (1°) and high- (0.25°) resolution EAMv1 configurations generally underestimate clouds in low latitudes and midlatitudes and overestimate clouds in the Arctic, although the error is smaller in the high-resolution model. The underestimate of clouds is due to the underestimate of optically thin to intermediate clouds, as EAMv1 generally overestimates optically intermediate to thick clouds. Other model errors include the largely underpredicted marine stratocumulus along the coasts and high clouds over the tropical deep convection regions. The underestimate of thin clouds results in too much longwave radiation being emitted to space and too little shortwave radiation being reflected back to space, while the overestimate of optically intermediate and thick clouds leads to too little longwave radiation being emitted to space and too much shortwave radiation being reflected back to space. EAMv1 shows better skill in reproducing the observed distribution of clouds and their properties and has smaller radiatively relevant errors in the distribution of clouds than most of the CFMIP1 and CFMIP2 models. It produces more supercooled liquid cloud fraction than CAM5 and most CMIP5 models primarily due to a new ice nucleation scheme and secondarily due to a reduction of the ice deposition growth rate.