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Evaluating CFSv2 Seasonal Hindcasts for the Period 1983-2010

Reference
Silva, G.A.M., Dutra, L.M.M., da Rocha, R.P., Ambrizzi, T. and Leiva, E. 2014. Preliminary analysis on the global features of the NCEP CFSv2 seasonal hindcasts. Advances in Meteorology 2014: 10.1155/2014/695067.
In the words of Silva et al. (2014), "Ocean-Atmosphere Global Climate Models (OAGCMs) have become indispensable tools for the climate sciences" and "many efforts have been made to improve [them] in recent years," the Climate Forecast System version 2 (CFSv2) model being "one example of such progress." which they then go on to describe and evaluate in considerable detail. Specifically, the authors state "the present study examined the area-average skill over the continents, the interannual variability, the global-mean state, and the main patterns of variability over the Equatorial Pacific and extratropics in both hemispheres produced by the CFSv2 model," which was done by comparing the model's hindcasts for Dec-Jan-Feb (DJF) and Jun-Jul-Aug (JJA) seasons of the 1983-2010 period with both "observations and reanalyses."

Based on their analysis the five Brazilian scientists report (1) "at the 0-month lead time ... large biases occur over the oceans," (2) "improvements in CFSv2 were not enough to eliminate the double-ITCZ [Intertropical Convergence Zone] bias during DJF," (3) there is a "warm SST [sea surface temperature] bias over eastern oceans during DJF and JJA," (4) for JJA there is an "SST cold bias over the central-equatorial Pacific," (5) "during DJF CFSv2 presents a cold bias in the troposphere, mainly over the central-eastern North Pacific," (6) there is a "strengthening of the subtropical jet that leads to precipitation overestimations by the persistence of low pressures over subtropical and mid-latitude regions," (7) "CFSv2 shows large precipitation biases over the eastern South Africa and Oceania," (8) there is a "wind-stress bias in the tropics," (9) "errors in the simulated Aleutian low seem to degrade the simulated NAM [Northern Annular Mode]," (10) "the wave pattern associated with the SAM [Southern Annular Mode] is not well reproduced by CFSv2," (11) there are "biases in the upper-level zonal wind over the tropics and mid-latitudes of the Southern Hemisphere," and (12) "the major spatial features related to the shape and orientation of SAM are not properly captured by CFSv2."

Silva et al.'s "overall evaluations" thus lead them to conclude "further investigations are still needed," and they say these studies "should be carried out to help in understanding further details the reasons for the CFSv2 deficiencies."

Archived 22 April 2014