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| Titel |
Interactions among drainage flows, gravity waves and turbulence: a BLLAST case study |
| VerfasserIn |
C. Román-Cascón, C. Yagüe, L. Mahrt, M. Sastre, G.-J. Steeneveld, E. Pardyjak, A. Boer, O. Hartogensis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 15 ; Nr. 15, no. 15 (2015-08-14), S.9031-9047 |
| Datensatznummer |
250119965
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| Publikation (Nr.) |
 copernicus.org/acp-15-9031-2015.pdf |
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| Zusammenfassung |
| The interactions among several stable-boundary-layer (SBL) processes
occurring just after the evening transition of 2 July 2011 have been analysed
using data from instruments deployed over the area of Lannemezan (France)
during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field
campaign. The near-calm situation of the afternoon was followed by the
formation of local shallow drainage flows (SDFs) of less than 10 m depth at different locations. The SDF stage
ended with the arrival of a stronger wind over a deeper layer more associated
with the mountain-plain circulation, which caused mixing and destruction of
the SDFs. Several gravity-wave-related oscillations were also observed on
different time series. Wavelet analyses and wave parameters were calculated
from high resolution and accurate surface pressure data of an array of
microbarometers. These waves propagated relatively long distances within the
SBL. The effects of these phenomena on turbulent parameters (friction
velocity and kinematic heat flux) have been studied through multi-resolution
flux decomposition methods performed on high frequency data from sonic
anemometers deployed at different heights and locations. With this method, we
were able to detect the different time-scales involved in each turbulent
parameter and separate them from wave contributions, which becomes very
important when choosing averaging-windows for surface flux computations using
eddy covariance methods. The extensive instrumentation allowed us to
highlight in detail the peculiarities of the surface turbulent parameters in
the SBL, where several of the noted processes were interacting and producing
important variations in turbulence with height and between sites along the
sloping terrain. |
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