Abstract
Abstract. Finding observational evidence of land surface and atmosphere interactions is crucial for understanding the spatial and temporal evolution of the boundary layer, as well as for model evaluation, and in particular for 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 from a scanning microwave radiometer (MWR) are used in a long-term study over 6 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 season- and direction-dependent IWV that is visible throughout the day. Comparisons with a satellite-derived spatial IWV distribution show good agreement for a selection of satellite overpasses during convective situations but no clear seasonal signal. With the help of a land use type classification and information on the topography, the main types of regions with a positive IWV deviation were determined to be agricultural fields and nearby open pit mines. Negative deviations occurred mainly above elevated forests and urban areas. In addition, high-resolution large-eddy simulations (LESs) are used to investigate changes in the water vapor and cloud fields for an altered land use input.
Highlights
Interactions between the land surface and the atmospheric boundary layer can have significant influences on the regional weather and climate
The height difference is corrected by assuming an exponential decrease in the humidity profile and by using the water vapor density obtained from measurements of temperature, humidity, and pressure from a weather sensor attached to the microwave radiometer (MWR), and the topography with a 200 m horizontal resolution
The findings presented here could be valuable for further studies using the Moderate Resolution Imaging Spectroradiometer (MODIS) products for assessing spatial integrated water vapor (IWV) differences, which is especially valuable for larger areas
Summary
Interactions between the land surface and the atmospheric boundary layer can have significant influences on the regional weather and climate. Investigating the influence of land use heterogeneity on boundary-layer characteristics, such as water vapor and clouds from long-term measurements, can play a key role in finding systematically significant patterns in relationships between the local land surface and atmosphere above. To address the question whether spatial water vapor distributions can be connected to land surface properties, this observational and modeling study focuses on the long-term pattern of azimuthal IWV deviations derived from satellite and ground-based measurements at the Jülich ObservatorY of Cloud Evolution (JOYCE; Löhnert et al, 2015) in western Germany (50.91◦ N, 6.41◦ E). For a better description of the state of the boundary layer during clearsky conditions and large-scale effects, the results are shown together with wind and turbulence statistics derived from Doppler lidar measurements during the MWR scans and a reanalysis product
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