Boundary-layer plumes over mountainous terrain in idealized large-eddy simulations

Jan Weinkaemmerer (Korresp. Autor*in), Matthias Göbel, Stefano Serafin, Ivan Bašták Ďurán, Jürg Schmidli

Veröffentlichungen: Beitrag in FachzeitschriftArtikelPeer Reviewed

Abstract

Coherent plume structures in the convective boundary layer over non-flat terrain are investigated using large-eddy simulation. A conditional sampling method based on the concentration of a decaying passive tracer is implemented in order to identify the boundary-layer plumes objectively. Conditional sampling allows quantification of the contribution of plume structures to the vertical transport of heat and moisture. A first set of simulations analyzes the flow over an idealized valley, where the terrain elevation only varies along one horizontal coordinate axis. In this case, vertical transport by coherent structures is the dominant contribution to the turbulent components of both heat and moisture flux. It is comparable in magnitude to the advective transport by the mean slope-wind circulation, although it is more important for heat than for moisture transport. A second set of simulations considers flow over terrain with a complex texture, drawn from an actual digital elevation model. In this case, conditional sampling is carried out by using a simple domain-decomposition approach. We demonstrate that thermal updrafts are generally more frequent on hill tops than over the surroundings, but they are less persistent on the windward sides when large-scale winds are present in the free atmosphere. Large-scale upper level winds tend to reduce the vertical moisture transport by the slope winds.

OriginalspracheEnglisch
Seiten (von - bis)3183-3197
Seitenumfang15
FachzeitschriftQuarterly Journal of the Royal Meteorological Society
Jahrgang149
Ausgabenummer757
Frühes Online-Datum9 Aug. 2023
DOIs
PublikationsstatusVeröffentlicht - 1 Okt. 2023

ÖFOS 2012

  • 105207 Gebirgsmeteorologie
  • 105206 Meteorologie

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