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Generation of free convection due to chances in the local circulation system

Title data

Eigenmann, Rafael ; Metzger, Stefan ; Foken, Thomas:
Generation of free convection due to chances in the local circulation system.
In: Atmospheric Chemistry and Physics Discussions. Vol. 9 (May 2009) Issue 3 . - pp. 11367-11411.
ISSN 1680-7375
DOI: https://doi.org/10.5194/acpd-9-11367-2009

Abstract in another language

Eddy-covariance and Sodar/RASS experimental measurement data of the COPS (Convective and Orographically-induced Precipitation Study) field campaign 2007 are used to investigate the generation of near-ground free convection events in the Kinzig valley, Black Forest, Southwest Germany. The measured high-quality turbulent flux data revealed free convection to be induced in situations where high buoyancy fluxes and a simultaneously occurring wind speed collapse were present. The minimum in wind speed – observable by the Sodar measurements through the whole vertical extension of the valley atmosphere – is the consequence of a thermally-induced valley wind system, which changes its wind direction from down to up-valley winds in the morning hours. Buoyant forces then dominate over shear forces within turbulence production. These situations are detected by the stability parameter (ratio of the measurementheight to the Obukhov length) calculated from directly measured turbulent fluxes. An analysis of the scales of turbulent motions during the free convection event using wavelet transform confirms the large-eddy scale character of the detected plume-like coherent structures. Regarding the entire COPS measurement period, free convection events (FCEs) in the morning hours occur on about 50% of all days.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER70526
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
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
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/18436