Development and Implementation of a Soil Moisture Perturbation Method for EPS Initial Conditions

The interaction between the surface and the lower troposphere determines the development of fluxes close to the ground. Soil moisture is of primary importance in determining the partition of energy between surface heat fluxes, thus affecting near-surface forecasts such as air temperature and precipitation forecasts. Ensemble forecasts usually suffer from a lack of variability among their members, which is mainly prominent near the surface rather than higher in the troposphere. In the framework of the Priority Project CONSENS of COSMO consortium, a method has been developed and adapted for perturbing soil moisture initial conditions. This method is based on the identification of the variability behavior in long data sets forming the model’s initial conditions—for each grid point of the domain—and determining the different members of the Ensemble Prediction Systems (EPS). The implementation of this method aims at ameliorating the variability of the solutions of COSMO EPS forecasts near the ground by exploring its impacts on the variability of the members for different forecast parameters, namely, 2 m air temperature, heat fluxes and accumulated precipitation.