Modified Description of Soil Processes vs. Quality of Numerical Weather Forecasts - “Bare Soil” Case

Soil and atmosphere boundary layer (ABL) interact with each other and influence on physical processes in soil and atmosphere. Current parameterization of soil physical processes in TERRA_ML (multilayer soil module of COSMO meteorological model) was prepared more than 40 years ago and did not give satisfactory forecast results. New parameterizations should involve physical processes in the soil (microphysics processes in soil, fluid dynamics in porous media, soil dynamics, etc.), water cycle in soil and soil-plant-water relation. The aim of this project was to improve current soil parameterization in the COSMO model, called “TERRA_ML”. The results of the work, related to the parameterization of physical processes of bare soil evaporation, vertical and horizontal water transport in soil and a runoff from soil layers, are presented in this paper. In order to eliminate underestimation of evaporation from soil in the afternoon and overestimation evaporation from soil in the morning a correction time-depending factor was also introduced. In this way, theoretical description of vertical water transport in soil is improved with temperature dependency of hydraulic diffusivity for different sort of soil.