Observations of the entrainment zone in a rapidly entraining boundary layer

G. S. Young, B. K. Cameron, E. E. Hebble

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14 Scopus citations


High-rate turbulence data collected by the National Center for Atmospheric Research Electra aircraft on 13 January 1998 over Lake Michigan during the Lake-Induced Convection Experiment are analyzed to explore the turbulence dynamics of the entrainment zone of a rapidly entraining convective boundary layer. Horizontal flight legs combined with the gentle slope of the lake-enhanced boundary layer top yield high-resolution profiles through the entrainment zone. Data analysis used a new maximally overlapping, subleg, Reynolds decomposition algorithm to compute first-, second-, and third-moment statistics for each flight leg. Then, a compositing algorithm using 25 bins took like statistics from each flight leg and created smoothly varying curves that captured the variation of each statistic across the upper mixed layer and entrainment zone. The analysis results reveal a conventional convective boundary layer below and a nonturbulent free atmosphere above a well-resolved entrainment zone. In the entrainment zone, temperature and moisture skewness curves show that the last identifiable free atmosphere effects extend down well below the zero crossing of heat flux. Third-moment statistics reveal considerable height dependence of the entrainment zone dynamics.

Original languageEnglish (US)
Pages (from-to)3145-3160
Number of pages16
JournalJournal of the Atmospheric Sciences
Issue number18
StatePublished - 2000

All Science Journal Classification (ASJC) codes

  • Atmospheric Science


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