Ansorge, Cedrick 
ORCID: 0000-0001-9913-3759
(2019).
Scale Dependence of Atmosphere-Surface Coupling Through Similarity Theory.
Bound.-Layer Meteor., 170 (1).
S. 1 - 28.
DORDRECHT:
SPRINGER.
ISSN 1573-1472
Abstract
Monin-Obukhov similarity theory (MOST) applies for homogeneous and stationary conditions but is used in ever more complex and heterogeneous configurations. Here, it is used to estimate the surface friction velocity u from the wind speed and temperature in the atmospheric surface layer (ASL). Filters of varying scale and direction are applied to wind speed and temperature in the ASL before MOST is used to estimate u. This procedure unveils the scale dependence of coupling between the ASL and the surface. Direct numerical simulation of turbulent Ekman flow above a smooth surface is used to explicitly resolve the near-wall dynamics. It is found that the viscous sub-layer may cease to exist, even in continuously turbulent neutral conditions, while the ASL covers more than one decade of variation in height. An underestimation in the variance of u estimated through MOST versus its actual variance is quantified as a function of height, averaging time, and length scale. For large filter scales, the variance exhibits a purely statistical convergencethere is no signature of long-term memory beyond the scale of coherent turbulent motion. Joint convergence of u estimated by MOST and the actual u is obtained for filter scales beyond several thousand wall units, and only for data filtered along both horizontal dimensions; the three-dimensional structure of the turbulence elements limits the convergence of data filtered along any of the single dimensions: time, the streamwise or spanwise direction. In stably stratified conditions, MOST is found to have no or negative skill in locally estimating ASL properties from u and should therefore only be applied to filtered quantities.
| Item Type: | Journal Article | ||||||||
| Creators: |
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| URN: | urn:nbn:de:hbz:38-140165 | ||||||||
| DOI: | 10.1007/s10546-018-0386-y | ||||||||
| Journal or Publication Title: | Bound.-Layer Meteor. | ||||||||
| Volume: | 170 | ||||||||
| Number: | 1 | ||||||||
| Page Range: | S. 1 - 28 | ||||||||
| Date: | 2019 | ||||||||
| Publisher: | SPRINGER | ||||||||
| Place of Publication: | DORDRECHT | ||||||||
| ISSN: | 1573-1472 | ||||||||
| Language: | English | ||||||||
| Faculty: | Faculty of Mathematics and Natural Sciences | ||||||||
| Divisions: | Faculty of Mathematics and Natural Sciences > Department of Geosciences > Institute for Geophysics and Meteorology | ||||||||
| Subjects: | no entry | ||||||||
| Uncontrolled Keywords: |
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| Refereed: | Yes | ||||||||
| URI: | http://kups.ub.uni-koeln.de/id/eprint/14016 |
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