Assessing the uncertainty of soil moisture impacts on convective precipitation using a new ensemble approach

Soil moisture influences the occurrence of convective precipitation. Therefore an accurate knowledge of soil moisture might be useful for an improved prediction of convective cells. But still the model uncertainty overshadows the impact of soil moisture in realistic cases even in 1 km resolution and therefore convection resolving models. Only drastic soil moisture changes can exhibit the model uncertainties but the systematic behaviour is still complex and depends strongly on the strength of soil moisture change. Here we performed seven experiments with modified soil moisture using an ensemble approach for each experiment. Only a 50 % soil moisture enhancement and a complete dried soil impact precipitation patterns considerably in structure, amplitude and location in certain analysis areas. Both, the enhanced and reduced soil moisture result in a reduced precipitation rate. Replacing the soil moisture by a realistic field from different days influences the precipitation insignificantly. We point out the need for uncertainty estimations in soil moisture studies.