Revealing differences in GCM representations of low clouds
Abstract
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.
- Publication:
-
Climate Dynamics
- Pub Date:
- January 2011
- DOI:
- 10.1007/s00382-009-0694-5
- Bibcode:
- 2011ClDy...36..385M
- Keywords:
-
- Climate model evaluation;
- Aquaplanet;
- Shallow cumulus;
- Trade-wind cumulus;
- Boundary layer clouds