Revealing differences in GCM representations of low clouds
Aquaplanet configurations of four atmospheric general circulation models (GCMs) are compared with standard, Earth-like configurations and observations. The focus here is on tropical, low-level clouds, which have been identified as important for estimates of climate sensitivity. Investigating the distribution of the monthly mean vertical velocity and lower-tropospheric stability, the aquaplanets are seen to capture the core of the distribution of the more Earth-like configurations, whose distributions are, in turn, similar to that of reanalysis data. By conditionally sampling over these distributions, low-cloud regimes are defined, separating shallow cumulus convection from stratocumulus. Within each regime, the GCMs produce similar large-scale environments, yet disparate depictions of the clouds. Aquaplanets lack stratocumulus because of their zonally symmetric boundary conditions, but produce extensive trade-wind regions populated by shallow cumulus clouds just like those in the Earth-like setting. The analysis shows that aquaplanets can be compared with observations, just as well as the Earth-like configuration, with the added ability to focus on particular regimes without complications from geographical or temporal biases.
document
http://n2t.net/ark:/85065/d7v989b7
eng
geoscientificInformation
Text
publication
2016-01-01T00:00:00Z
publication
2009-10-19T00:00:00Z
An edited version of this paper was published by Springer. Copyright 2009 Brian Medeiros and Bjorn Stevens.
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