Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 6 2008 10.5194/acp-8-1701-2008 http://www.atmos-chem-phys.net/8/1701/2008/ http://www.atmos-chem-phys.net/8/1701/2008/acp-8-1701-2008.html http://www.atmos-chem-phys.net/8/1701/2008/acp-8-1701-2008.pdf 1701 1712 2008-03-20 Technical Note: Description and assessment of a nudged version of the new dynamics Unified Model P. J. Telford paul.telford@atm.ch.cam.ac.uk P. Braesicke O. Morgenstern J. A. Pyle University of Cambridge, Cambridge NCAS-Climate, UK We present a "nudged" version of the Met Office general circulation model, the Unified Model. We constrain this global climate model using ERA-40 re-analysis data with the aim of reproducing the observed "weather" over a year from September 1999. Quantitative assessments are made of its performance, focusing on dynamical aspects of nudging and demonstrating that the "weather" is well simulated. 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