Quarterly Journal of the Royal Meteorological Society Q. J. R. Meteorol. Soc. 136: 1145 – 1160, July 2010 Part A The ECMWF model climate: Recent progress through improved physical parametrizations T. Jung, a *G. Balsamo, a P. Bechtold, a A. C. M. Beljaars, a M. K¨ ohler, a M. J. Miller, a J.-J. Morcrette, a A. Orr, a,c M. J. Rodwell a and A. M. Tompkins a,b a European Centre for Medium-Range Weather Forecasts, Reading, UK b International Centre for Theoretical Physics, Trieste, Italy c British Antarctic Survey, Cambridge, UK *Correspondence to: T. Jung, ECMWF, Shinfield Park, Reading, Berkshire RG1 9AX, UK. E-mail: jung@ecmwf.int The progress achieved since 2005 in simulating today’s climate with the European Centre for Medium-Range Weather Forecasts (ECMWF) model through improved physical parametrizations is described. Results are based on climate integrations at an intermediate horizontal resolution (T L 159) using major model versions employed operationally at ECMWF since June 2005. Recent improvements to the physical parametrization package are shown to substantially reduce long- standing systematic model deficiencies in the tropical precipitation, convectively coupled tropical waves, and circulation features in the Northern Hemisphere Extratropics including synoptic-scale variability and Euro-Atlantic blocking. The climate integrations are augmented by a set of monthly forecast experiments. By considering the atmospheric response in a seamless sense, i.e. from time-scales of hours to many months, an attempt is made to understand the impact of changes to the convection and radiation schemes. Overall, the largest and mostly beneficial impact results from the introduction of a major revision to the convection scheme made in November 2007. This is true for systematic errors in the Tropics and Extratropics over a wide range of time-scales as well as for the short-range and medium-range deterministic forecast skill over the Northern Hemisphere. Copyright c  2010 Royal Meteorological Society Key Words: systematic error; precipitation; atmospheric circulation; blocking; synoptic activity; convectively coupled waves; seamless approach; tropical–extratropical interaction Received 3 February 2009; Revised 31 March 2010; Accepted 11 April 2010; Published online in Wiley InterScience 9 July 2010 Citation: Jung T, Balsamo G, Bechtold P, Beljaars ACM, K¨ ohler M, Miller MJ, Morcrette J-J, Orr A, Rodwell MJ, Tompkins AM. 2010. The ECMWF model climate: Recent progress through improved physical parametrizations. Q. J. R. Meteorol. Soc. 136: 1145 – 1160. DOI:10.1002/qj.634 1. Introduction A frequently asked question is how well state-of-the- art atmospheric models simulate today’s climate and how systematic errors have changed in time though improvements in model formulation (e.g. Jung, 2005; Reichler and Kim, 2008). An assessment of three generations of coupled models by Reichler and Kim (2008) shows that atmospheric components of state-of-the-art models are certainly not perfect but better than their predecessors. The authors explain this in terms of improvements in physical parametrizations and increased horizontal and vertical resolution. A comprehensive study of systematic errors in the ECMWF model and their evolution from the 1980s has been presented by Jung and Tompkins (2003) and Jung (2005). These studies reveal substantial systematic error reduction in the medium-range (about 3–10 days), particularly during the 1980s and 1990s. However, even the model versions used in the early 2000s still produced Copyright c  2010 Royal Meteorological Society