01684nas a2200205 4500008004100000245005300041210005300094260001900147300000700166520111500173100001701288700002001305700002101325700001301346700002301359700001701382700002001399700002201419856003701441 2009 eng d00aStochastic parametrization and model uncertainty0 aStochastic parametrization and model uncertainty bECMWFc10/2009 a423 aStochastic parametrization provides a methodology for representing model uncertainty in ensemble forecasts, and also has the capability of reducing systematic error through the concept of nonlinear noise-induced rectification. The stochastically perturbed parametrization tendencies scheme and the stochastic backscatter scheme are described and their impact on medium-range forecast skill is discussed. The impact of these schemes on ensemble data assimilation and in seasonal forecasting is also considered. In all cases, the results are positive. Validation of the form of these stochastic parametrizations can be found by coarse-grain budgets of high resolution (e.g. cloud-resolving) models; some results are shown. Stochastic parametrization has been pioneered at ECMWF over the last decade, and now most operational centres use stochastic parametrization in their operational ensemble prediction systems - these are briefly discussed. The seamless prediction paradigm implies that serious consideration should now be given to the use of stochastic parametrization in next generation Earth System Models.1 aPalmer, T.N.1 aBuizza, Roberto1 aDoblas-Reyes, F.1 aJung, T.1 aLeutbecher, Martin1 aShutts, G.J.1 aSteinheimer, M.1 aWeisheimer, Antje uhttps://www.ecmwf.int/node/11577