The Low-Resolution CCSM4

• Published in: Journal of climate Vol. 25; no. 12; pp. 3993 - 4014
• Main Authors: Shields, Christine A., Bailey, David A., Danabasoglu, Gokhan, Jochum, Markus, Kiehl, Jeffrey T., Levis, Samuel, Park, Sungsu
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 15.06.2012
• Subjects: Archives & records; Arctic sea ice; Atmosphere; Atmospheric models; Bias; Climate; Climate models; Climate system; Climate variability; Climatology. Bioclimatology. Climate change; Cost control; Earth, ocean, space; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; Estimates; Exact sciences and technology; External geophysics; Geophysics. Techniques, methods, instrumentation and models; Heat transport; Ice cover; Meteorology; Modeling; Modelling; Northern Hemisphere; Oceans; Paleoclimatology; Physics; Resolution; Runoff; Sea ice; Sea ice thickness; Sea surface; Sea surface temperature; Sea transportation; Simulations; Southern Hemisphere; Southern Oscillation; SPECIAL Community Climate System Model CCSM4 COLLECTION; Surface temperature; Temperature anomalies; Topography; Variability; Wind stress; Zonal winds; Performance evaluation; Validation; Climatology; Coupled model; General circulation models; sensitivity analysis; Observation data; Climate models; digital simulation; Low resolution
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/jcli-d-11-00260.1

The low-resolution version of the Community Climate System Model, version 4 (CCSM4) is a computationally efficient alternative to the intermediate and standard resolution versions of this fully coupled climate system model. It employs an atmospheric horizontal grid of 3.75° × 3.75° and 26 levels in the vertical with a spectral dynamical core (T31) and an oceanic horizontal grid that consists of a nominal 3° resolution with 60 levels in the vertical. This low-resolution version (T31x3) can be used for a variety of applications including long equilibrium simulations, development work, and sensitivity studies. The T31x3 model is validated for modern conditions by comparing to available observations. Significant problems exist for Northern Hemisphere Arctic locales where sea ice extent and thickness are excessive. This is partially due to low heat transport in T31x3, which translates into a globally averaged sea surface temperature (SST) bias of −1.54°C compared to observational estimates from the 1870–99 historical record and a bias of −1.26°C compared to observations from the 1986–2005 historical record. Maximum zonal wind stress magnitude in the Southern Hemisphere matches observational estimates over the ocean, although its placement is incorrectly displaced equatorward. Aspects of climate variability in T31x3 compare to observed variability, especially so for ENSO where the amplitude and period approximate observations. T31x3 surface temperature anomaly trends for the twentieth century also follow observations. An examination of the T31x3 model relative to the intermediate CCSM4 resolution (finite volume dynamical core 1.9° × 2.5°) for preindustrial conditions shows the T31x3 model approximates this solution for climate state and variability metrics examined here.