ALBERT

Description: Finding observational evidence of land surface atmosphere interactions is crucial for understanding the spatial and temporal evolution of the boundary layer, as well as for model evaluation, in particular large-eddy simulation (LES) models. In this study, the influence of a heterogeneous land surface on the spatial distribution of atmospheric water vapor is assessed. Ground-based remote sensing measurements of a scanning microwave radiometer (MWR) are used in a long-term study over six years to characterize spatial heterogeneities in integrated water vapor (IWV) during clear sky conditions at the Jülich Observatory for Cloud Evolution (JOYCE). The resulting deviations from the mean of the scans reveal a direction-dependent IWV that is visible throughout the day. Comparisons to a satellite derived spatial IWV distribution show a good agreement for a selection of 61 satellite overpasses during convective situations. With the help of a land use type classification and information on the topography, the main type for the regions with a positive IWV deviation was determined to be agricultural fields and nearby open pit mines. Negative deviations occurred mainly above elevated forests and urban areas. The observational results are in agreement with a high resolution large-eddy simulation (LES), which was used in addition to investigate changes in surface fluxes and the water vapor and cloud field for an altered land use input.