Modelling of evapotranspiration at field and landscape scales. Abstract

The overall aim of this project is to couple a non-hydrostatic atmospheric model (ARPS) to an integrated hydrological model (MIKE SHE) to investigate atmospheric and hydrological feedbacks at different scales. To ensure a consistent coupling a new land-surface component based on a modified Shuttleworth-Wallace scheme was implemented in MIKE SHE. To validate the new land-surface component at different scales, the hydrological model was applied to an intensively monitored 10 km2 agricultural area in Denmark with a resolution of 40 meter. The model is forced with half-hourly metorological observations from a nearby weather station. Detailed land-use and soil maps were used to set up the model. Leaf area index was derived from NDVI (Normalized Difference Vegetation Index) images. To validate the model at field scale the simulated evapotranspiration rates were compared to eddy-covariance observations from three 2-m masts representing fluxes from grass, winter wheat and spring barley. Observations from 40-m mast representing a mixture of the land-use classes in the model domain were used to validate the model at the larger scale. Good agreement was found at both the field and landscape scale. Further validation is being carried out with satellite data. Initial results from the coupled model will also be presented.