Improving the physical consistency of ensemble forecasts by using SPP in the IFS
Leutbecher, Martin ; Lang, Simon ; Lock, Sarah-Jane ; Roberts, Christopher D. ; Tsiringakis, Aristofanis
Ensemble forecasts need to account for uncertainties in both initial conditions and the forecast model. Since 1998, the latter uncertainties have been represented in ECMWF's Integrated Forecasting System (IFS) via the Stochastically Perturbed Parametrization Tendency scheme (SPPT; Buizza et al., 1999). This scheme is also referred to as 'stochastic physics'. It has been revised several times. SPPT has played an important role through increasing the ensemble spread and boosting the probabilistic skill of ECMWF ensemble forecasts over the past 25 years (see Lock et al., 2019, for details of the operational SPPT configuration). In IFS Cycle 49r1, which will be implemented in November 2024, SPPT will be replaced by the Stochastically Perturbed Parametrizations (SPP) scheme in all ensemble applications. SPP has been developed over several years (Ollinaho et al., 2017; Lang et al., 2021). It represents model uncertainties closer to the sources of errors. The remainder of the article explains the motivation for this revision and how the new scheme works, and it sets out the impacts expected from the revision of the model uncertainty representation.</p>
Accès à la notice sur le site du portail documentaire de Météo-France