Assessing clouds using satellite observations through three generations of global atmosphere models

The most recent generation, represented by two distinct branches of development, exhibits some regional regressions in the cloud representation; in particular the southern ocean shows a positive bias in cloud cover. The two branches of model development show how choices during model development, both structural and parametric, lead to different cloud climatologies. Several evaluation strategies are used to quantify the spatial errors in terms of the large-scale circulation and the cloud structure.

The Earth mover's distance is proposed as a useful error metric for the passive satellite data products that provide cloud-top pressure-optical depth histograms. The cloud errors identified here may contribute to the high climate sensitivity in the Community Earth System Model, version 2 and in the Energy Exascale Earth System Model, version 1.