Dynamical Properties of MOS Forecasts: Analysis of the ECMWF Operational Forecasting System

Abstract The dynamical properties of ECMWF operational forecasts corrected by a (linear) model output statistics (MOS) technique are investigated, in light of the analysis performed in the context of low-order chaotic systems. Based on the latter work, the respective roles of the initial condition and model errors on the forecasts can be disentangled. For the temperature forecasted by the ECMWF model over Belgium, it is found that (i) the error amplification arising from the presence of uncertainties in the initial conditions dominates the error dynamics of the “free” atmosphere and (ii) the temperature at 2 m can be partly corrected by the use of the (linear) MOS technique (as expected from earlier works), suggesting that model errors and systematic initial condition biases dominate at the surface. In the latter case, the respective amplitudes of the model errors and systematic initial condition biases corrected by MOS depend on the location of the synoptic station. In addition, for a two-observables MOS...

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