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Coherent structures and flux contribution over an inhomogeneously irrigated cotton field

Title data

Zhang, Yu ; Liu, Heping ; Foken, Thomas ; Williams, Quinton L. ; Mauder, Matthias ; Thomas, Christoph:
Coherent structures and flux contribution over an inhomogeneously irrigated cotton field.
In: Theoretical and Applied Climatology. Vol. 103 (2011) Issue 1/2 . - pp. 119-131.
ISSN 0177-798X
DOI: https://doi.org/10.1007/s00704-010-0287-6

Abstract in another language

The turbulence data measured at two levels (i.e., 8.7 and 2.7 m) in the Energy Balance Experiment (EBEX), which was conducted in San Joaquin Valley in California during the period from July 20 to August 24, 2000, are used to study the characteristics of coherent structures over an irrigated cotton field. Patch-to-patch irrigation in the field generated the dry-to-wet horizontal advection and the oasis effects, leading to the development of a stably internal boundary layer (SIBL) in the late mornings or the early afternoons. The SIBL persisted in the rest of the afternoons. Under this circumstance, a near-neutral atmospheric surface layer (ASL) developed during the period with a stratification transition from the unstable to stable conditions during the daytime. Therefore, EBEX provides us with unique datasets to investigate the features of coherent structures that were generated over the patches upstream and passed by our site in the unstable ASL, the near-neutral ASL, and the SIBL. We use an objective detection technique and the conditional average method that is developed based on the wavelet analysis. Our data reveal some consistencies and inconsistencies in the characteristics of coherent structures as compared with previous studies. Ramp-like structures and sweep–ejection cycles under the daytime SIBL have similar patterns to those under the nocturnal stable ASL. However, some features (i.e., intermittence) are different from those under the nocturnal stable ASL. Under the three stratifications, thermal and mechanical factors in the ASL perform differently in affecting the ramp intensity for different quantities (i.e., velocity components, temperature, and specific humidity), leading to coherent structures that modulate turbulence flow and alter turbulent transfer differently. It is also found that coherent structures contribute about 10–20% to the total fluxes in our case 44with different flux contributions under three stratifications and with higher transporting efficiency in sensible heat flux than latent heat and momentum fluxes.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER83376
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Micrometeorology
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Professorship Micrometeorology > Professorship Micrometeorology - Univ.-Prof. Dr. Christoph K. Thomas
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 24 Apr 2015 11:56
Last Modified: 24 Apr 2015 11:56
URI: https://eref.uni-bayreuth.de/id/eprint/11428