Editorial Type:
Article
Article Type:
Research Article

Mesoscale Simulation of Supercritical, Subcritical, and Transcritical Flow along Coastal Topography

Stephen D. Burk Marine Meteorology Division, Naval Research Laboratory, Monterey, California

Search for other papers by Stephen D. Burk in
Current site
Google Scholar
PubMed Close
,
Tracy Haack Marine Meteorology Division, Naval Research Laboratory, Monterey, California

Search for other papers by Tracy Haack in
Current site
Google Scholar
PubMed Close
, and
R. M. Samelson College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon

Search for other papers by R. M. Samelson in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Aug 1999
DOI:
https://doi.org/10.1175/1520-0469(1999)056<2780:MSOSSA>2.0.CO;2
Page(s):
2780–2795
Restricted access

We are aware of a technical issue preventing figures and tables from showing in some newly published articles in the full-text HTML view.
While we are resolving the problem, please use the online PDF version of these articles to view figures and tables.

Abstract

A mesoscale atmospheric model is used to address the characteristics of stratified flow bounded by a side wall along a varying coastline. Initial Froude number values are varied through alteration of marine inversion strength, permitting examination of supercritical, subcritical, and transcritical flow regimes encountering several coastal configurations. Consistent with shallow water models, sharp drops in boundary layer depth and flow acceleration occur in flow rounding convex bends; however, significant flow response occurs in the stratified layer aloft, which is unexplained by conventional shallow water theory. The strongest flow acceleration occurs in the transcritical case while, regardless of inversion strength, the deformation of the isentropes aloft shows general structural similarity.

Advection of horizontal momentum is an important component of the horizontal force balance. A simulation having several coastline bends exhibits a detached, oblique hydraulic jump upwind of a concave bend that strongly blocks the flow. For the single-bend case, a shallow water similarity theory for stratified flow provides qualitative, and partial quantitative, agreement with the mesoscale model, in the boundary layer and aloft. Horizontal structure functions for these similarity solutions satisfy a set of equivalent shallow water equations. This comparison provides a new perspective on previous shallow water models of supercritical flow around coastal bends and suggests that the existence of the supercritical flow response may depend more on the presence of a low-level jet than on a sharp boundary layer inversion.

Corresponding author address: Stephen D. Burk, Marine Meteorology Division, Naval Research Laboratory, 7 Grace Hopper Avenue, Monterey, CA 93943-5502.

Abstract

A mesoscale atmospheric model is used to address the characteristics of stratified flow bounded by a side wall along a varying coastline. Initial Froude number values are varied through alteration of marine inversion strength, permitting examination of supercritical, subcritical, and transcritical flow regimes encountering several coastal configurations. Consistent with shallow water models, sharp drops in boundary layer depth and flow acceleration occur in flow rounding convex bends; however, significant flow response occurs in the stratified layer aloft, which is unexplained by conventional shallow water theory. The strongest flow acceleration occurs in the transcritical case while, regardless of inversion strength, the deformation of the isentropes aloft shows general structural similarity.

Advection of horizontal momentum is an important component of the horizontal force balance. A simulation having several coastline bends exhibits a detached, oblique hydraulic jump upwind of a concave bend that strongly blocks the flow. For the single-bend case, a shallow water similarity theory for stratified flow provides qualitative, and partial quantitative, agreement with the mesoscale model, in the boundary layer and aloft. Horizontal structure functions for these similarity solutions satisfy a set of equivalent shallow water equations. This comparison provides a new perspective on previous shallow water models of supercritical flow around coastal bends and suggests that the existence of the supercritical flow response may depend more on the presence of a low-level jet than on a sharp boundary layer inversion.

Corresponding author address: Stephen D. Burk, Marine Meteorology Division, Naval Research Laboratory, 7 Grace Hopper Avenue, Monterey, CA 93943-5502.

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

  • Bridger, A. F. C., W. C. Brick, and P. F. Lester, 1993: The structure of the marine inversion layer off the central California coast: Mesoscale conditions. Mon. Wea. Rev.,121, 335–351.

  • Burk, S. D., and W. T. Thompson, 1996: The summertime low-level jet and marine boundary layer structure along the California coast. Mon. Wea. Rev.,124, 668–686.

  • Doyle, J. D., 1997: The influence of mesoscale orography on a coastal jet and rainband. Mon. Wea. Rev.,125, 1465–1488.

  • Durran, D. R., 1986: Another look at downslope windstorms. Part I:The development of analogs of supercritical flow in an infinitely deep, continuously stratified fluid. J. Atmos. Sci.,43, 2527–2543.

  • ——, 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.

  • ——, and J. Klemp, 1987: Another look at downslope windstorms. Part II: Nonlinear amplification beneath wave-overturning layers. J. Atmos. Sci.,44, 3402–3412.

  • Elliott, D. L., and J. J. O’Brien, 1977: Observational studies of the marine boundary layer over an upwelling region. Mon. Wea. Rev.,105, 748–761.

  • Enfield, D. B., 1981: Thermally driven wind variability in the planetary boundary layer above Lima, Peru. J. Geophys. Res.,86, 2005–2016.

  • Enriquez, A. G., and C. A. Friehe, 1995: Effects of wind stress and wind stress curl variability on coastal upwelling. J. Phys. Oceanogr.,25, 1651–1671.

  • Freeman, J. C., 1950: The wind field of the equatorial east Pacific as a Prandtl-Meyer expansion. Bull. Amer. Meteor. Soc.,31, 303–304.

  • Gill, A. E., 1982: Atmosphere–Ocean Dynamics. Academic Press, 662 pp.

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

  • Ippen, A. T., 1951: Mechanics of supercritical flow. Trans. Amer. Soc. Civil Eng.,116, 268–295.

  • Long, R. R., 1953: Some aspects of the flow of stratified fluids I. A theoretical investigation. Tellus,5, 42–58.

  • Rogers, D. P., and Coauthors, 1998: Highlights of coastal waves 1996. Bull. Amer. Meteor. Soc.,79, 1307–1326.

  • Rogerson, A. M., 1999: Transcritical flows in the coastal marine atmospheric boundary layer. J. Atmos. Sci.,56, 2761–2779.

  • Samelson, R. M., 1992: Supercritical marine-layer flow along a smoothly varying coastline. J. Atmos. Sci.,49, 1571–1584.

  • ——, and S. J. Lentz, 1994: The horizontal momentum balance in the marine atmospheric boundary layer during CODE-2. J. Atmos. Sci.,51, 3745–3757.

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

  • ——, and J. Sun, 1987: Generalized hydraulic solutions pertaining to severe downslope winds. J. Atmos. Sci.,44, 2934–2939.

  • Stull, R. B., 1988: An Introduction to Boundary Layer Meteorology. Kluwer Academic, 666 pp.

  • Thompson, W. T., T. Haack, J. D. Doyle, and S. D. Burk, 1997: A nonhydrostatic mesoscale simulation of the 10–11 June 1994 coastally trapped wind reversal. Mon. Wea. Rev.,125, 3211–3230.

  • Winant, C. D., C. E. Dorman, C. A. Friehe, and R. C. Beardsley, 1988: The marine layer off northern California: An example of supercritical channel flow. J. Atmos. Sci.,45, 3588–3605.

  • Yih, C.-S., 1969: A class of solutions for steady stratified flows. J. Fluid Mech.,36, 75–85.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 799 535 167
PDF Downloads 144 50 1