A technique using the wavelet transform to identify and isolate coherent structures in the planetary boundary layer

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A dominant feature of the convective planetary boundary layer (PBL) is the presence of coherent structures often referred to as thermal plumes. These are regions of buoyant, rising air whose maximum height is limited by the capping inversion at the top of the mixed layer. They range in diameter from 0.05 to 5 km or more, scale with the height of the mixed layer (z{sub i}), are the large-scale source of energy input to the turbulence spectrum, and provide the mechanism for transferring energy from the surface through the mixed layer and into the capping inversion. When conditions are appropriate, ... continued below

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5 p.

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Coulter, R.L. & Li, B.L. May 1, 1995.

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  • Coulter, R.L. Argonne National Lab., IL (United States)
  • Li, B.L. Texas A&M Univ., College Station, TX (United States). Dept. of Industrial Engineering

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A dominant feature of the convective planetary boundary layer (PBL) is the presence of coherent structures often referred to as thermal plumes. These are regions of buoyant, rising air whose maximum height is limited by the capping inversion at the top of the mixed layer. They range in diameter from 0.05 to 5 km or more, scale with the height of the mixed layer (z{sub i}), are the large-scale source of energy input to the turbulence spectrum, and provide the mechanism for transferring energy from the surface through the mixed layer and into the capping inversion. When conditions are appropriate, fair-weather cumulus clouds develop at the tops of the thermal plumes. In this sense, small cumulus clouds provide a visual description of the size, location, and lifetime of mature, active thermal plumes in a deep mixed layer. Plume development is not limited to plumes associated with cumulus clouds. Although the horizontal pattern of thermals is often apparently randomly oriented, Ferrare et al. showed that thermals can be organized into {open_quotes}thermal streets,{close_quotes} similar to cloud streets, but without clouds. The authors also used scanning lidar data to show that the horizontal cross section of thermals is roughly elliptical, with the major axis along the direction of the wind shear vector. Traveling with the mean wind, thermal plumes act as a conduit for heat and moisture between the surface and the lower troposphere. Thermal plumes can be defined either by patterns of rising air or as organized regions of enhanced {open_quotes}thermal turbulence{close_quotes} that can be depicted by large values of the temperature structure parameter, C{sub T}{sup 2} which can be evaluated with remote sensing instruments such as radar profilers and sodars. This more general description includes some regions of downward moving air and entrainment into the plume.

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5 p.

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OSTI as DE95011956

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  • 11. symposium on boundary layers and turbulence, Charlotte, NC (United States), 27-31 Mar 1995

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  • Other: DE95011956
  • Report No.: ANL/ER/CP--84064
  • Report No.: CONF-950381--3
  • Grant Number: W-31109-ENG-38
  • Office of Scientific & Technical Information Report Number: 67718
  • Archival Resource Key: ark:/67531/metadc709637

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  • May 1, 1995

Added to The UNT Digital Library

  • Sept. 12, 2015, 6:31 a.m.

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  • Dec. 15, 2015, 12:49 p.m.

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Coulter, R.L. & Li, B.L. A technique using the wavelet transform to identify and isolate coherent structures in the planetary boundary layer, article, May 1, 1995; Illinois. (digital.library.unt.edu/ark:/67531/metadc709637/: accessed September 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.