Testing Version 4 of the Community Climate System Model
Grodsky, S.A., Carton, J.A., Nigam, S. and Okumura, Y.M. 2012. Tropical Atlantic biases in CCSM4. Journal of Climate 25: 3684-3701.
In an effort designed to "revisit" this unsolved problem, Grodsky et al. utilized the Community Climate System Model, version 4 (CCSM4; Gent et al., 2011), which is a coupled climate model that simultaneously simulates Earth's atmosphere, ocean, land surface and sea ice processes. This they did by comparing 20th-century runs forced by time-varying solar output, greenhouse gas, volcanic and other aerosol concentrations for the period 1850-2005 with observed (real world) monthly variability computed from observational analyses during the 26-year period 1980-2005.
In the enlightening words of the four researchers, they report finding that (1) the "atmospheric component of CCSM4 has abnormally intense surface subtropical high pressure systems and abnormally low polar low pressure systems," (2) "in the tropics and subtropics, the trade wind winds are 1-2 m/sec too strong [and] latent heat loss is too large," (3) "sea surface temperature in the southeast has a warm bias [due in part to] erroneously weak equatorial winds," (4) "the warm bias evident along the coast of southern Africa is also partly a result of insufficient local upwelling," (5) "excess radiation is evident in the south stratocumulus region of up to 60 W/m2," (6) there is "excess precipitation in the Southern Hemisphere," and (7) "errors in cloud parameterization lead to "massively excess solar radiation in austral winter and spring in CCSM4."
Meet the new model. Same as the old model. And don't get fooled again.
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