Measurements of thermal updraft intensity over complex terrain using American white pelicans and a simple boundary-layer forecast model

Harlan D. Shannon, George Spencer Young, Michael A. Yates, Mark R. Fuller, William S. Seegar

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

An examination of boundary-layer meteorological and avian aerodynamic theories suggests that soaring birds can be used to measure the magnitude of vertical air motions within the boundary layer. These theories are applied to obtain mixed-layer normalized thermal updraft intensity over both flat and complex terrain from the climb rates of soaring American white pelicans and from diagnostic boundary-layer model-produced estimates of the boundary-layer depth zi and the convective velocity scale w*. Comparison of the flatland data with the profiles of normalized updraft velocity obtained from previous studies reveals that the pelican-derived measurements of thermal updraft intensity are in close agreement with those obtained using traditional research aircraft and large eddy simulation (LES) in the height range of 0.2 to 0.8 zi. Given the success of this method, the profiles of thermal vertical velocity over the flatland and the nearby mountains are compared. This comparison shows that these profiles are statistically indistinguishable over this height range, indicating that the profile for thermal updraft intensity varies little over this sample of complex terrain. These observations support the findings of a recent LES study that explored the turbulent structure of the boundary layer using a range of terrain specifications. For terrain similar in scale to that encountered in this study, results of the LES suggest that the terrain caused less than an 11% variation in the standard deviation of vertical velocity.

Original languageEnglish (US)
Pages (from-to)167-199
Number of pages33
JournalBoundary-Layer Meteorology
Volume104
Issue number2
DOIs
StatePublished - Aug 1 2002

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

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