Accession Number : ADA260300


Title :   Turbulent Microfronts


Descriptive Note : Final rept. 15 Jun 1989-15 Oct 1992


Corporate Author : OREGON STATE UNIV CORVALLIS


Personal Author(s) : Mahrt, Larry


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a260300.pdf


Report Date : 05 Nov 1992


Pagination or Media Count : 9


Abstract : The research work under this contract studied turbulence structures in the atmospheric boundary layer by focussing on microfronts. Microfronts are zones of sharp gradients which occur at the leading edge of wind gusts and upstream edges of thermals. The present work indicates that microfronts also result from convergence zones induced by horseshoe vortices and longitudinal roll vortices. The microfronts and their parent eddy structures account for the majority of the flux in the boundary layer, and in cases of strong winds, contribute to wind damage and structural fatique. However, existing methods, such as Fourier spectra, cannot be used to study microfronts which are local and aperiodic. In fact, microfronts and boundary layer eddies have been traditionally studied in terms of subjective conditional sampling. To avoid this subjectivity, we have developed objective techniques to study atmospheric turbulence from the microfront point of view. These include new methods for computing spectra and filtering data. The techniques developed in this work have then been used to study coherent structures and their transport in the atmospheric boundary layer.


Descriptors :   *ATMOSPHERIC MOTION , *TURBULENT BOUNDARY LAYER , *FRONTS(METEOROLOGY) , ROLL , DAMAGE , VORTICES , TRANSPORT , CONVERGENCE , GRADIENTS , CONVERGENCE ZONES , FILTRATION , LEADING EDGES , GUSTS , SPECTRA , WIND , BOUNDARY LAYER , TURBULENCE


Subject Categories : Meteorology


Distribution Statement : APPROVED FOR PUBLIC RELEASE