A Regional Reanalysis with a Coupled Soil-Vegetation-Atmosphere-Transfer Model on the Convective Scale

Reanalyses provide fields of weather and climate parameters, aiming at physical consistency in space and time, as well as between variables, by combining model physics and assimilation of measurements. They are usually intended for longer time periods and global coverage, therefore using a coarsely meshed spatial grid to delimitate the computational effort. Due to the coarse spatial resolution, local and small scale processes, such as convective events, are not well represented. It is expected that future reanalyses, will provide higher spatial resolution and will be based to a greater extent on fully coupled models, representing additional transfers between soil, vegetation and the atmosphere. The new Terrestrial Systems Modeling Platform (TerrSysMP) is able to reproduce processes within the atmosphere, surface and the groundwater compartments. TerrSysMP was developed within the Transregional Collaborative Research Centre 32 (TR32) and is a scale consistent fully coupled modeling system, which is composed of the atmospheric model COSMO, the surface model CLM3.5 (Community Land Model) and the 3-dimensional hydrological model ParFlow. Earlier studies already prove that TerrSysMP provides a rectified hydrological balance in the coupled system and well reproduces the energy and water fluxes between the atmosphere, vegetation and ground, especially on small scales. In this study TerrSysMP is set-up with a horizontal grid-spacing of approx. 1 km for the atmosphere and a finer resolution for the surface and sub-surface (approx. 500 m) for an area of 150x150 km in Central Europe. Since the area includes various measurement stations operated by TR32, numerous recordings from the atmosphere to the ground are available for comparison with the modeled parameters and state variables. This study evaluates the added value of simulations with the fully coupled model TerrSysMP against existing atmospheric reanalyses for Central Europe, based on the COSMO model. The study focuses on convective events in order to prove the added value of a fully coupled model in representing small scale processes.