Editorial Type:
Article
Article Type:
Research Article

A Theoretical Study of Mountain Barrier Jets over Sloping Valleys

Qin Xu Naval Research Laboratory, Monterey, California

Search for other papers by Qin Xu in
Current site
Google Scholar
PubMed Close
,
Ming Liu Naval Research Laboratory, Monterey, California

Search for other papers by Ming Liu in
Current site
Google Scholar
PubMed Close
, and
Douglas L. Westphal Naval Research Laboratory, Monterey, California

Search for other papers by Douglas L. Westphal in
Current site
Google Scholar
PubMed Close
Print Publication:
01 May 2000
DOI:
https://doi.org/10.1175/1520-0469(2000)057<1393:ATSOMB>2.0.CO;2
Page(s):
1393–1405
Restricted access

Abstract

A shallow-water model is developed to examine the dynamics of mountain-barrier jets over a mesoscale sloping valley between two mountain ridges. In this model, the cold air trapped in the valley is represented by a shallow-water layer that is coupled with the upper-layer flow through a free-slip interface. The pressure gradient exerted from the upper layer plus the pressure gradient generated by the sloping cold layer itself drive the cold air down the valley forming a jet against the surface friction. In the cross-valley direction, the jet-induced Coriolis force is balanced by the pressure gradient force. For a given cross-valley terrain profile, the solution is controlled by eight dimensional environmental parameters. In the nondimensional space, the solution is controlled only by three parameters: the Froude number modified by the ratio between the valley width and the Rossby radius of deformation, the surface drag coefficient normalized by the ratio between the valley depth and the inertial radius, and the upper-layer cross-valley pressure gradient scaled by the lower-layer along-valley pressure gradient. Analytical solutions are obtained for a given cross-valley terrain profile, and the results quantify the dependence of the jet intensity and cross-valley structure on the environmental parameters. The theoretical results are also compared with numerical model simulations.

Corresponding author address: Dr. Qin Xu, National Severe Storms Laboratory, 1313 Halley Circle, Norman, OK 73069.

Email: qxu@tornado.gcn.ou.edu

Abstract

A shallow-water model is developed to examine the dynamics of mountain-barrier jets over a mesoscale sloping valley between two mountain ridges. In this model, the cold air trapped in the valley is represented by a shallow-water layer that is coupled with the upper-layer flow through a free-slip interface. The pressure gradient exerted from the upper layer plus the pressure gradient generated by the sloping cold layer itself drive the cold air down the valley forming a jet against the surface friction. In the cross-valley direction, the jet-induced Coriolis force is balanced by the pressure gradient force. For a given cross-valley terrain profile, the solution is controlled by eight dimensional environmental parameters. In the nondimensional space, the solution is controlled only by three parameters: the Froude number modified by the ratio between the valley width and the Rossby radius of deformation, the surface drag coefficient normalized by the ratio between the valley depth and the inertial radius, and the upper-layer cross-valley pressure gradient scaled by the lower-layer along-valley pressure gradient. Analytical solutions are obtained for a given cross-valley terrain profile, and the results quantify the dependence of the jet intensity and cross-valley structure on the environmental parameters. The theoretical results are also compared with numerical model simulations.

Corresponding author address: Dr. Qin Xu, National Severe Storms Laboratory, 1313 Halley Circle, Norman, OK 73069.

Email: qxu@tornado.gcn.ou.edu

Save
Cover Journal of the Atmospheric Sciences
Journal of the Atmospheric Sciences

  • Baines, P. G., and B. P. Leonard, 1989: The effects of rotation on flow of a single layer over a ridge. Quart. J. Roy. Meteor. Soc.,115, 293–308.

  • Bell, G. D., and L. F. Bosart, 1988: Appalachian cold-air damming. Mon. Wea. Rev.,116, 137–161.

  • Braun, S. A., R. Rotunno, and J. B. Klemp, 1999: Effects of coastal orography on landfalling cold fronts. Part I: Dry, inviscid dynamics. J. Atmos. Sci.,56, 517–533.

  • Condray, P. M., and R. T. Edson, 1988: Persian Gulf transmittance study in the 8–12 micron band. USAF Environmental Technical Applications Center Tech. Note USAFETAC/TN-88/003, 85 pp. [Available from Environmental Technical Applications Center, Scott Air Force Base, IL 62225.].

  • Douglas, M. W., 1995: The summertime low-level jet over the Gulf of California. Mon. Wea. Rev.,123, 2334–2347.

  • Doyle, J. D., and T. T. Warner, 1990: Mesoscale coastal processes during GALE IOP 2. Mon. Wea. Rev.,118, 283–308.

  • Dunn, L., 1987: Cold air damming by the Front Range of the Colorado Rockies and its relationship to locally heavy snows. Wea. Forecasting,2, 177–189.

  • ——, 1992: Evidence of ascent in a sloped barrier jet and an associated heavy-snow band. Mon. Wea. Rev.,120, 914–924.

  • Durran, D. R., 1992: Two-layer solutions to Long’s equation for vertically propagating mountain waves—How good is linear-theory? Quart. J. Roy. Meteor. Soc.,118, 415–433.

  • Forbes, G. S., R. A. Anthes, and D. W. Thomson, 1987: Synoptic and mesoscale aspects of an Appalachian ice storm associated with cold-air damming. Mon. Wea. Rev.,115, 564–591.

  • Fritsch, J. M., J. Kapolka, and P. A. Hirschberg, 1992: The effects of subcloud-layer diabatic processes on cold air damming. J. Atmos. Sci.,49, 49–70.

  • Hodur, R. M., 1997: The Naval Research Laboratory’s Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS). Mon. Wea. Rev.,125, 1414–1430.

  • Holt, T. R., 1996: Mesoscale forcing of a boundary layer jet along the California coast. J. Geophys. Res.,101 (D2), 4235–4254.

  • Hoskins, B. J., and F. P. Bretherton, 1972: Atmospheric frontogenesis models: Mathematical formulation and solution. J. Atmos. Sci.,29, 11–37.

  • Jackson, P. L., and D. G. Steyn, 1994a: Gap winds in a fjord. Part I:Observations and numerical simulation. Mon. Wea. Rev.,122, 2645–2665.

  • ——, and ——, 1994b: Gap winds in a fjord. Part II: Hydraulic analog. Mon. Wea. Rev.,122, 2666–2676.

  • Lackmann, G. M., and J. E. Overland, 1989: Atmospheric structure and momentum balance during a gap-wind event in Shelikof Strait, Alaska. Mon. Wea. Rev.,117, 1817–1833.

  • Liu, M., D. L. Westphal, T. R. Holt, and Q. Xu, 2000: Numerical simulation of a low-level jet over complex terrain in southern Iran. Mon. Wea. Rev.,128, 1309–1327.

  • Macklin, S. A., N. A. Bond, and J. P. Walker, 1990: Structure of a low-level jet over lower Cook Inlet, Alaska. Mon. Wea. Rev.,118, 2568–2578.

  • Mass, C. F., S. Businger, M. D. Albright, and Z. A. Tucker, 1995: A windstorm in the lee of a gap in a coastal mountain barrier. Mon. Wea. Rev.,123, 315–331.

  • Nielsen, J. W., 1989: The formation of New England coastal fronts. Mon. Wea. Rev.,117, 1380–1401.

  • Overland, J. E., and B. A. Walter Jr., 1981: Gap winds in the Strait of Juan de Fuca. Mon. Wea. Rev.,109, 2221–2233.

  • ——, and N. Bond, 1993: The influence of coastal orography: The Yakutat storm. Mon. Wea. Rev.,121, 1388–1397.

  • Perrone, T. J., 1979: Winter Shamal in the Persian Gulf. NAVENVPREDRSCHFAC, Tech. Rep. TR 79-06, 160 pp. [Available from Naval Research Laboratory, Monterey, CA 93943.].

  • Pierrehumbert, R. T., and B. Wyman, 1985: Upstream effect of mesoscale mountains. J. Atmos. Sci.,42, 977–1003.

  • Richwien, B. A., 1980: The damming effect of the southern Appalachians. Natl. Wea. Dig.,5 (1), 2–12.

  • Schwerdtfeger, W., 1975: The effect of the Antarctic Peninsula on the temperature regime of the Weddell Sea. Mon. Wea. Rev.,103, 45–51.

  • Shutts, G. J., 1987: The semigeostrophic weir: A simple model of flow over mountain barriers. J. Atmos. Sci.,44, 2018–2030.

  • Smith, R. B., 1982: Synoptic observations and theory of orographically disturbed wind and pressure. J. Atmos. Sci.,39, 60–70.

  • ——, 1985: On severe downslope winds. J. Atmos. Sci.,42, 2597–2603.

  • Stauffer, D. R., and T. T. Warner, 1987: A numerical study of Appalachian cold-air damming and coastal frontogenesis. Mon. Wea. Rev.,115, 799–821.

  • Thomas, C. S., 1987: The Iranian hostage rescue attempt. DTIC SELECTED, AD-A183, 395, 22 pp. [Available from U.S. Army War College, Carlisle Barracks, PA 17013.].

  • Walters, K. R., and W. F. Sjoberg, 1988: The Persian Gulf region—A Climatological study. USAFETAC TN-88/002, 62 pp. [Available from USAF Environmental Technical Applications Center, Scott AFB, IL 62225.].

  • Xu, Q., 1990: A theoretical study of cold air damming. J. Atmos. Sci.,47, 2969–2985.

  • ——, and S. Gao, 1995: An analytic model of cold air damming and its applications. J. Atmos. Sci.,52, 353–366.

  • ——, ——, and B. H. Fiedler, 1996: A theoretical study of cold air damming caused by upstream blocking of stratified flow. J. Atmos. Sci.,53, 312–326.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 142 15 1
PDF Downloads 35 6 0