Two-layer stratified flow past a valley

AMS Citation:
Rotunno, R., and M. Lehner, 2016: Two-layer stratified flow past a valley. Journal of the Atmospheric Sciences, 73, 4065-4076, doi:10.1175/JAS-D-16-0132.1.
Resource Type:article
Title:Two-layer stratified flow past a valley
Abstract: Observations and models of nocturnal katabatic winds indicate strong low-level stability with much weaker stability aloft. When such winds encounter an embedded depression in an otherwise smooth sloping plane, the flow responds in a manner that is largely describable by the inviscid fluid dynamics of stratified flow. Building on earlier work, the present study presents a series of numerical simulations based on the simplest nontrivial idealization relevant to the observations: the height-independent flow of a two-layer stratified fluid past a two-dimensional valley. Stratified flow past a valley has received much less attention than the related problem of stratified flow past a hill. Hence, the present paper gives a detailed review of existing theory and fills a few gaps along the way. The theory is used as an interpretive guide to an extensive set of numerical simulations. The solutions exhibit a variety of behaviors that depend on the nondimensional input parameters. These behaviors range from complete flow through the valley to valley-flow stagnation to situations involving internal wave breaking, lee waves, and quasi-stationary waves in the valley. A diagram is presented that organizes the solutions into flow regimes as a function of the nondimensional input parameters.
Peer Review:Refereed
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OpenSky citable URL: ark:/85065/d7kh0q08
Publisher's Version: 10.1175/JAS-D-16-0132.1
  • Richard Rotunno - NCAR/UCAR
  • Manuela Lehner
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