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How Does the Choice of the Lower Boundary Conditions in Large-Eddy Simulations Affect the Development of Dispersive Fluxes Near the Surface?

Wanner, L. 1; De Roo, F.; Sühring, M.; Mauder, M. 1,2
1 Institut für Meteorologie und Klimaforschung – Atmosphärische Umweltforschung (IMK-IFU), Karlsruher Institut für Technologie (KIT)
2 Institut für Geographie und Geoökologie (IFGG), Karlsruher Institut für Technologie (KIT)

Abstract:

Large-eddy simulations (LES) are an important tool for investigating the longstanding energy-balance-closure problem, as they provide continuous, spatially-distributed information about turbulent flow at a high temporal resolution. Former LES studies reproduced an energy-balance gap similar to the observations in the field typically amounting to 10–30% for heights on the order of 100 m in convective boundary layers even above homogeneous surfaces. The underestimation is caused by dispersive fluxes associated with large-scale turbulent organized structures that are not captured by single-tower measurements. However, the gap typically vanishes near the surface, i.e. at typical eddy-covariance measurement heights below 20 m, contrary to the findings from field measurements. In this study, we aim to find a LES set-up that can represent the correct magnitude of the energy-balance gap close to the surface. Therefore, we use a nested two-way coupled LES, with a fine grid that allows us to resolve fluxes and atmospheric structures at typical eddy-covariance measurement heights of 20 m. Under different stability regimes we compare three different options for lower boundary conditions featuring grassland and forest surfaces, i.e. ... mehr

Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung – Atmosphärische Umweltforschung (IMK-IFU)
Institut für Geographie und Geoökologie (IFGG)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2021
Sprache Englisch
Identifikator ISSN: 0006-8314, 1573-1472
KITopen-ID: 1000137068
HGF-Programm 12.11.11 (POF IV, LK 01) Urban Climate and Air Quality
Erschienen in Boundary-Layer Meteorology
Verlag Springer
Band 182
Seiten 1-27
Vorab online veröffentlicht am 10.08.2021
Nachgewiesen in Scopus
Dimensions
Web of Science
Relationen in KITopen

Verlagsausgabe §
DOI: 10.5445/IR/1000137068
Veröffentlicht am 12.09.2021
Originalveröffentlichung
DOI: 10.1007/s10546-021-00649-7
Scopus
Zitationen: 8
Web of Science
Zitationen: 5
Dimensions
Zitationen: 8
Seitenaufrufe: 174
seit 12.09.2021
Downloads: 157
seit 14.09.2021
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