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Open AccessArticle

Study of Realistic Urban Boundary Layer Turbulence with High-Resolution Large-Eddy Simulation

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Atmospheric Dispersion Modelling, Atmospheric Composition Research, Finnish Meteorological Institute, 00560 Helsinki, Finland
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Institute of Atmospheric and Earth System Research, Faculty of Science, University of Helsinki, 00560 Helsinki, Finland
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Department of Mathematics and Statistics, University of Helsinki, 00560 Helsinki, Finland
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OP Financial Group, 00510 Helsinki, Finland
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Department of Forest Sciences, University of Helsinki, 00790 Helsinki, Finland
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Helsinki Institute of Sustainability Science, University of Helsinki, 00014 Helsinki, Finland
*
Author to whom correspondence should be addressed.
Current address: Erik Palménin Aukio 1, 00560 Helsinki, Finland.
Atmosphere 2020, 11(2), 201; https://doi.org/10.3390/atmos11020201
Received: 30 December 2019 / Revised: 27 January 2020 / Accepted: 5 February 2020 / Published: 13 February 2020
(This article belongs to the Section Atmospheric Techniques, Instruments, and Modeling)
This study examines the statistical predictability of local wind conditions in a real urban environment under realistic atmospheric boundary layer conditions by means of Large-Eddy Simulation (LES). The computational domain features a highly detailed description of a densely built coastal downtown area, which includes vegetation. A multi-scale nested LES modelling approach is utilized to achieve a setup where a fully developed boundary layer flow, which is also allowed to form and evolve very large-scale turbulent motions, becomes incident with the urban surface. Under these nonideal conditions, the local scale predictability and result sensitivity to central modelling choices are scrutinized via comparative techniques. Joint time–frequency analysis with wavelets is exploited to aid targeted filtering of the problematic large-scale motions, while concepts of information entropy and divergence are exploited to perform a deep probing comparison of local urban canopy turbulence signals. The study demonstrates the utility of wavelet analysis and information theory in urban turbulence research while emphasizing the importance of grid resolution when local scale predictability, particularly close to the pedestrian level, is sought. In densely built urban environments, the level of detail of vegetation drag modelling description is deemed most significant in the immediate vicinity of the trees. View Full-Text
Keywords: large-eddy simulation; turbulence; urban boundary layer; urban canopy; wavelet analysis; information entropy large-eddy simulation; turbulence; urban boundary layer; urban canopy; wavelet analysis; information entropy
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Auvinen, M.; Boi, S.; Hellsten, A.; Tanhuanpää, T.; Järvi, L. Study of Realistic Urban Boundary Layer Turbulence with High-Resolution Large-Eddy Simulation. Atmosphere 2020, 11, 201.

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