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Turbulence spectra and cospectra under the influence on large eddies in the Energy Balance EXperiment (EBEX)

Title data

Zhang, Yu ; Liu, Heping ; Foken, Thomas ; Williams, Quinton L. ; Liu, Shuahua ; Mauder, Matthias ; Liebethal, Claudia:
Turbulence spectra and cospectra under the influence on large eddies in the Energy Balance EXperiment (EBEX).
In: Boundary-Layer Meteorology. Vol. 136 (August 2010) Issue 2 . - pp. 235-251.
ISSN 1573-1472
DOI: https://doi.org/10.1007/s10546-010-9504-1

Abstract in another language

During the Energy Balance EXperiment, the patch-by-patch, flood irrigation in a flat cotton field created an underlying surface with heterogeneous soil moisture, leading to a dry (warm)-to-wet (cool) transition within the cotton field under northerly winds. Moreover, the existence of an extremely dry, large bare soil area upstream beyond the cotton field created an even larger step transition from the bare soil region to the cotton field. We investigated the turbulence spectra and cospectra in the atmospheric surface layer (ASL) that was disturbed by large eddies generated over regions upstream and also influenced by horizontal advection. In the morning, the ASL was unstable while in the afternoon a stable internal boundary layer was observed at the site. Therefore, the turbulence data at 2.7 and 8.7 m are interpreted and compared in terms of interactions between large eddies and locally generated turbulence under two atmospheric conditions: the unstable ASL beneath the convective boundary layer (CBL) (hereafter the unstable condition) and the stable ASL beneath the CBL (hereafter the stable condition). We identified the influences of multiple sizes of large eddies on ASL turbulence under both stratifications; these large eddies with multiple sizes were produced over the dry patches and dry, large bare soil areas upstream. As a consequence of the disturbance of large eddies, the broadening, erratic variability, and deviation of spectra and cospectra, relative to those described by Monin–Obukhov similarity theory, are evident in the low- to mid-frequencies. Transfer of momentum, heat, and water vapour by large eddies is distinctly observed from the turbulence cospectra and leads to significant run-to-run variations of residuals of the surface energy balance closure. Our results indicate that these large eddies have greater influences on turbulence at higher levels compared to lower levels, and in the unstable ASL compared to the stable ASL.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER83529
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Former Professors > Professorship Micrometeorology - Univ.-Prof. Dr. Thomas Foken
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Former Professors
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 21 Aug 2015 06:49
Last Modified: 21 Aug 2015 06:49
URI: https://eref.uni-bayreuth.de/id/eprint/18424