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contributor authorWroblewski, Donald E.
contributor authorCoté, Owen R.
contributor authorHacker, Jorg M.
contributor authorDobosy, Ron J.
date accessioned2017-06-09T16:53:47Z
date available2017-06-09T16:53:47Z
date copyright2007/07/01
date issued2007
identifier issn0022-4928
identifier otherams-76139.pdf
identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4218553
description abstractCliff?ramp patterns (CR) are a common feature of scalar turbulence, characterized by a sharp temperature increase (cliff) followed by a more gradual temperature decrease (ramp). Aircraft measurements obtained from NOAA best aircraft turbulence probes (BAT) were used to characterize and compare CR patterns observed under stably stratified conditions in the upper troposphere, a region for which there are few such studies. Experimental data were analyzed for three locations, one over Wales and two over southern Australia, the latter in correspondence with the Southern Hemisphere winter subtropical jet stream. Comparison of observed CR patterns with published direct numerical simulations (DNS) revealed that they were likely signatures of Kelvin?Helmholtz (KH) billows, with the ramps associated with the well-mixed billows and the cliffs marking the highly stretched braids. Strong correlation between potential temperature and horizontal velocity supported the KH link, though expected correlations with vertical velocity were not observed. The temperature fronts associated with the cliffs were oriented in a direction approximately normal to the mean wind direction. Locally high values of temperature structure constant near these fronts were associated with steep temperature gradients across the fronts; this may be misleading in the context of electromagnetic propagation, suggesting a false positive indication of high levels of small-scale turbulence that would not correspond to scintillation effects. Billow aspect ratios, braid angles, and length scales were estimated from the data and comparisons with published DNS provided a means for assessing the stage of evolution of the KH billows and the initial Richardson number of the layer.
publisherAmerican Meteorological Society
titleCliff–Ramp Patterns and Kelvin–Helmholtz Billows in Stably Stratified Shear Flow in the Upper Troposphere: Analysis of Aircraft Measurements
typeJournal Paper
journal volume64
journal issue7
journal titleJournal of the Atmospheric Sciences
identifier doi10.1175/JAS3956.1
journal fristpage2521
journal lastpage2539
treeJournal of the Atmospheric Sciences:;2007:;Volume( 064 ):;issue: 007
contenttypeFulltext


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