Editorial Type:
Article
Article Type:
Research Article

A Case Study of the Nocturnal Boundary Layer Evolution on a Slope at the Foot of a Desert Mountain

Manuela Lehner Department of Atmospheric Sciences, University of Utah, Salt Lake City, Utah

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C. David Whiteman Department of Atmospheric Sciences, University of Utah, Salt Lake City, Utah

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Sebastian W. Hoch Department of Atmospheric Sciences, University of Utah, Salt Lake City, Utah

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Derek Jensen Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah

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Eric R. Pardyjak Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah

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Laura S. Leo Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana

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Silvana Di Sabatino Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana

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Harindra J. S. Fernando Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana

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Print Publication:
01 Apr 2015
Collections:
Mountain Terrain Atmospheric Modeling and Observations (MATERHORN)
DOI:
https://doi.org/10.1175/JAMC-D-14-0223.1
Page(s):
732–751
Restricted access

Abstract

Observations were taken on an east-facing sidewall at the foot of a desert mountain that borders a large valley, as part of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) field program at Dugway Proving Ground in Utah. A case study of nocturnal boundary layer development is presented for a night in mid-May when tethered-balloon measurements were taken to supplement other MATERHORN field measurements. The boundary layer development over the slope could be divided into three distinct phases during this night: 1) The evening transition from daytime upslope/up-valley winds to nighttime downslope winds was governed by the propagation of the shadow front. Because of the combination of complex topography at the site and the solar angle at this time of year, the shadow moved down the sidewall from approximately northwest to southeast, with the flow transition closely following the shadow front. 2) The flow transition was followed by a 3–4-h period of almost steady-state boundary layer conditions, with a shallow slope-parallel surface inversion and a pronounced downslope flow with a jet maximum located within the surface-based inversion. The shallow slope boundary layer was very sensitive to ambient flows, resulting in several small disturbances. 3) After approximately 2300 mountain standard time, the inversion that had formed over the adjacent valley repeatedly sloshed up the mountain sidewall, disturbing local downslope flows and causing rapid temperature drops.

Corresponding author address: Manuela Lehner, Dept. of Atmospheric Sciences, University of Utah, 135 S 1460 E, Rm. 819, Salt Lake City, UT 84112-0110. E-mail: manuela.lehner@utah.edu

This article is included in the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) special collection.

Abstract

Observations were taken on an east-facing sidewall at the foot of a desert mountain that borders a large valley, as part of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) field program at Dugway Proving Ground in Utah. A case study of nocturnal boundary layer development is presented for a night in mid-May when tethered-balloon measurements were taken to supplement other MATERHORN field measurements. The boundary layer development over the slope could be divided into three distinct phases during this night: 1) The evening transition from daytime upslope/up-valley winds to nighttime downslope winds was governed by the propagation of the shadow front. Because of the combination of complex topography at the site and the solar angle at this time of year, the shadow moved down the sidewall from approximately northwest to southeast, with the flow transition closely following the shadow front. 2) The flow transition was followed by a 3–4-h period of almost steady-state boundary layer conditions, with a shallow slope-parallel surface inversion and a pronounced downslope flow with a jet maximum located within the surface-based inversion. The shallow slope boundary layer was very sensitive to ambient flows, resulting in several small disturbances. 3) After approximately 2300 mountain standard time, the inversion that had formed over the adjacent valley repeatedly sloshed up the mountain sidewall, disturbing local downslope flows and causing rapid temperature drops.

Corresponding author address: Manuela Lehner, Dept. of Atmospheric Sciences, University of Utah, 135 S 1460 E, Rm. 819, Salt Lake City, UT 84112-0110. E-mail: manuela.lehner@utah.edu

This article is included in the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) special collection.

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