The ECMWF model climate: recent progress through improved physical parametrizations



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 (TL159) 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 © 2010 Royal Meteorological Society