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Stratocumulus Clouds of the Subtropical North and South Atlantic

Evan, A.T., Allen, R.J., Bennartz, R. and Vimont, D.J. 2013. The modification of sea surface temperature anomaly linear damping time scales by stratocumulus clouds. Journal of Climate 26: 3619-3630.
In the words of Evan et al. (2013), "stratocumulus (Sc) cloud cover is a persistent feature of the subtropical North and South Atlantic," and that "it is well known that Sc cloud cover increases with decreasing temperatures of the underlying sea surface and that an increase in cloud cover will cool the surface temperatures via increasing the local albedo, otherwise known as the Sc feedback." Against this backdrop, Evan et al. used real-world observations to "quantify the magnitude and spatial structure of the Sc feedback in the tropical-extratropical Atlantic Ocean," as well as to "investigate the role of the Sc feedback in shaping the evolution of coupled modes of variability there," especially when utilizing CMIP3 models.

In discussing their findings the four researchers report that "most models have negative biases in the mean state of Sc cloud cover and do not reproduce the observed spatial structure of Atlantic Sc clouds." In addition, they indicate that "while the majority of models exhibit some agreement with observations in the meridional structure of the Sc feedback, the vast majority of models underestimate the dependence of Sc cloud cover on the underlying sea surface temperature."

Once again, we have a situation where important aspects of both cloud type and cloud cover are simply not portrayed to an acceptable degree of real-world faithfulness in the "majority" - or better make that the "vast" majority - of CMIP3 models.

Archived 1 October 2013