Editorial Type:
Article
Article Type:
Research Article

Synoptic Responses to Mountain Gravity Waves Encountering Directional Critical Levels

Armel Martin Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Supérieure, Paris, France

Search for other papers by Armel Martin in
Current site
Google Scholar
PubMed Close
and
François Lott Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Supérieure, Paris, France

Search for other papers by François Lott in
Current site
Google Scholar
PubMed Close
Print Publication:
01 Mar 2007
DOI:
https://doi.org/10.1175/JAS3873.1
Page(s):
828–848
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 heuristic model is used to study the synoptic response to mountain gravity waves (GWs) absorbed at directional critical levels. The model is a semigeostrophic version of the Eady model for baroclinic instability adapted by Smith to study lee cyclogenesis. The GWs exert a force on the large-scale flow where they encounter directional critical levels. This force is taken into account in the model herein and produces potential vorticity (PV) anomalies in the midtroposphere.

First, the authors consider the case of an idealized mountain range such that the orographic variance is well separated between small- and large-scale contributions. In the absence of tropopause, the PV produced by the GW force has a surface impact that is significant compared to the surface response due to the large scales. For a cold front, the GW force produces a trough over the mountain and a larger-amplitude ridge immediately downstream. It opposes somehow to the response due to the large scales of the mountain range, which is anticyclonic aloft and cyclonic downstream. For a warm front, the GW force produces a ridge over the mountain and a trough downstream; hence it reinforces the response due to the large scales.

Second, the robustness of the previous results is verified by a series of sensitivity tests. The authors change the specifications of the mountain range and of the background flow. They also repeat some experiments by including baroclinic instabilities, or by using the quasigeostrophic approximation. Finally, they consider the case of a small-scale orographic spectrum representative of the Alps.

The significance of the results is discussed in the context of GW parameterization in the general circulation models. The results may also help to interpret the complex PV structures occurring when mountain gravity waves break in a baroclinic environment.

Corresponding author address: Dr. Armel Martin, Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Supérieure, 24, rue Lhomond, 75235 Paris CEDEX 05, France. Email: martin@lmd.ens.fr

Abstract

A heuristic model is used to study the synoptic response to mountain gravity waves (GWs) absorbed at directional critical levels. The model is a semigeostrophic version of the Eady model for baroclinic instability adapted by Smith to study lee cyclogenesis. The GWs exert a force on the large-scale flow where they encounter directional critical levels. This force is taken into account in the model herein and produces potential vorticity (PV) anomalies in the midtroposphere.

First, the authors consider the case of an idealized mountain range such that the orographic variance is well separated between small- and large-scale contributions. In the absence of tropopause, the PV produced by the GW force has a surface impact that is significant compared to the surface response due to the large scales. For a cold front, the GW force produces a trough over the mountain and a larger-amplitude ridge immediately downstream. It opposes somehow to the response due to the large scales of the mountain range, which is anticyclonic aloft and cyclonic downstream. For a warm front, the GW force produces a ridge over the mountain and a trough downstream; hence it reinforces the response due to the large scales.

Second, the robustness of the previous results is verified by a series of sensitivity tests. The authors change the specifications of the mountain range and of the background flow. They also repeat some experiments by including baroclinic instabilities, or by using the quasigeostrophic approximation. Finally, they consider the case of a small-scale orographic spectrum representative of the Alps.

The significance of the results is discussed in the context of GW parameterization in the general circulation models. The results may also help to interpret the complex PV structures occurring when mountain gravity waves break in a baroclinic environment.

Corresponding author address: Dr. Armel Martin, Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Supérieure, 24, rue Lhomond, 75235 Paris CEDEX 05, France. Email: martin@lmd.ens.fr

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

  • Aebischer, U., and C. Schär, 1998: Low-level potential vorticity and cyclogenesis to the lee of the Alps. J. Atmos. Sci., 55 , 186–207.

    • Search Google Scholar
    • Export Citation

  • Binder, P., and C. Schär, 1996: MAP design proprosal. Meteo Swiss, 77 pp. [Available online at http://www.map.meteoswiss.ch/map-doc/prop/MDP.pdf.].

  • Boer, G. J., N. A. McFarlane, R. Laprise, J. D. Henderson, and J-P. Blanchet, 1984: The Canadian Climate Center spectral atmospheric general circulation model. Atmos.–Ocean, 22 , 397–429.

    • Search Google Scholar
    • Export Citation

  • Booker, J. R., and F. P. Bretherton, 1967: The critical layer for internal gravity waves in a shear flow. J. Fluid Mech., 27 , 513–539.

    • Search Google Scholar
    • Export Citation

  • Bougeault, P., and Coauthors, 2001: The MAP special observing period. Bull. Amer. Meteor. Soc., 82 , 433–462.

  • Bretherton, F. P., 1969: Momentum transport by gravity waves. Quart. J. Roy. Meteor. Soc., 95 , 213–243.

  • Broad, A. S., 1999: Do orographic gravity waves break in flows with uniform wind direction turning with height? Quart. J. Roy. Meteor. Soc., 125 , 1695–1714.

    • Search Google Scholar
    • Export Citation

  • Bühler, O., and M. E. McIntyre, 2005: Wave capture and wave-vortex duality. J. Fluid Mech., 534 , 67–95.

  • Davis, C. A., 1997: The modification of baroclinic waves by the Rocky Mountains. J. Atmos. Sci., 54 , 848–868.

  • Eliassen, A., and E. Palm, 1961: On the transfer of energy in the stationary mountain waves. Geofys. Publ., 22 , 1–23.

  • Fantini, M., and S. Davolio, 2001: Instability of neutral Eady waves and orography. J. Atmos. Sci., 58 , 1146–1154.

  • Flamant, C., E. Richard, C. Schär, R. Rotunno, L. Nance, M. Sprenger, and R. Benoit, 2004: The wake south of the Alps: Dynamics and structure of the lee-side flow and secondary potential vorticity banners. Quart. J. Roy. Meteor. Soc., 130 , 1275–1303.

    • Search Google Scholar
    • Export Citation

  • Gregory, D., G. J. Shutts, and J. R. Mitchell, 1998: A new gravity-wave-drag scheme incorporating anisotropic orography and low-level wave-breaking: Impact upon the climate of the UK Meteorological Office unified model. Quart. J. Roy. Meteor. Soc., 124 , 463–493.

    • Search Google Scholar
    • Export Citation

  • Gross, B. D., 1994: Frontal interaction with isolated orography. J. Atmos. Sci., 51 , 1480–1496.

  • Haynes, P. H., and M. E. McIntyre, 1987: On the evolution of vorticity and potential vorticity in the presence of diabatic heating and frictional or other forces. J. Atmos. Sci., 44 , 828–841.

    • Search Google Scholar
    • Export Citation

  • Hoinka, K. P., E. Richard, G. Poberaj, R. Busen, J-L. Caccia, A. Fix, and H. Mannstein, 2003: Analysis of a potential-vorticity streamer crossing the Alps during MAP IOP-15 on 6 November 1999. Quart. J. Roy. Meteor. Soc., 129 , 609–632.

    • Search Google Scholar
    • Export Citation

  • Hoskins, B. J., 1975: The geostrophic momentum approximation and the semi-geostrophic equations. J. Atmos. Sci., 32 , 233–242.

  • Hoskins, B. J., M. E. McIntyre, and A. W. Robertson, 1985: On the use and significance of isentropic potential vorticity maps. Quart. J. Roy. Meteor. Soc., 111 , 877–946.

    • Search Google Scholar
    • Export Citation

  • Jiang, Q., and J. D. Doyle, 2004: Gravity wave breaking over the central Alps: Role of complex terrain. J. Atmos. Sci., 61 , 2249–2266.

    • Search Google Scholar
    • Export Citation

  • Liniger, M. A., and H. C. Davies, 2003: Substructure of a map streamer. Quart. J. Roy. Meteor. Soc., 129 , 633–651.

  • Lott, F., 1999: Alleviation of stationary biases in a GCM through a mountain drag parameterization scheme and a simple representation of mountain lift forces. Mon. Wea. Rev., 127 , 788–801.

    • Search Google Scholar
    • Export Citation

  • Lott, F., 2003: Large scale flow response to short gravity waves breaking in a rotating shear flow. J. Atmos. Sci., 60 , 1691–1704.

  • Lott, F., and M. J. Miller, 1997: A new subgrid-scale orographic parametrization: Its formulation and testing. Quart. J. Roy. Meteor. Soc., 123 , 101–127.

    • Search Google Scholar
    • Export Citation

  • McFarlane, N. A., 1987: The effect of orographically excited gravity wave drag on the general circulation of the lower stratosphere and troposphere. J. Atmos. Sci., 44 , 1775–1800.

    • Search Google Scholar
    • Export Citation

  • Messinger, M., and R. Pierrehumbert, 1986: Alpine lee cyclogenesis: Numerical simulation and theory. Scientific Results of the Alpine Experiment, GARP Publications Series 27, Vol. I, WMO/International Council of Scientific Unions, 141–165.

  • Miller, M. J., T. N. Palmer, and R. Swinbank, 1989: Parametrization and influence of subgridscale orography in general circulation and numerical weather prediction models. Meteor. Atmos. Phys., 40 , 84–109.

    • Search Google Scholar
    • Export Citation

  • National Geophysical Data Center, cited. 2006: 2-Minute Gridded Global Relief Data (ETOPO2v2). NOAA/NESDIS/NGCD. [Available online at http://www.ngdc.noaa.gov/mgg/fliers/06mgg01.html.].

  • Palmer, T. N., G. J. Shutts, and R. Swinbank, 1986: Alleviation of a systematic westerly bias in general circulation and numerical weather prediction models through an orographic gravity wave drag parametrization. Quart. J. Roy. Meteor. Soc., 112 , 1001–1039.

    • Search Google Scholar
    • Export Citation

  • Phillips, D. S., 1984: Analytical surface pressure and drag for linear hydrostatic flow over three-dimensional elliptical mountains. J. Atmos. Sci., 41 , 1073–1084.

    • Search Google Scholar
    • Export Citation

  • Pierrehumbert, R. T., 1985: A theoretical model of orographically modified cyclogenesis. J. Atmos. Sci., 42 , 1244–1258.

  • Plougonven, R., D. J. Muraki, and C. Snyder, 2005: A baroclinic instability that couples balanced motions and gravity waves. J. Atmos. Sci., 62 , 1545–1559.

    • Search Google Scholar
    • Export Citation

  • Scavuzzo, C. M., M. A. Lamfri, H. Teitelbaum, and F. Lott, 1998: A study of the low frequency inertio-gravity waves observed during PYREX. J. Geophys. Res., 103 , D2. 1747–1758.

    • Search Google Scholar
    • Export Citation

  • Schär, C., 1990: Quasi-geostrophic lee cyclogenesis. J. Atmos. Sci., 47 , 3044–3066.

  • Schär, C., and D. R. Durran, 1997: Vortex formation and vortex shedding in continuously stratified flows past isolated topography. J. Atmos. Sci., 54 , 533–554.

    • Search Google Scholar
    • Export Citation

  • Schär, C., M. Sprenger, D. Lüthi, Q. Jiang, R. B. Smith, and R. Benoit, 2003: Structure and dynamics of an Alpine potential-vorticity banner. Quart. J. Roy. Meteor. Soc., 129 , 825–855.

    • Search Google Scholar
    • Export Citation

  • Scinocca, J. F., and N. A. McFarlane, 2000: The parametrization of drag induced by stratitified flow over anisotropic orography. Quart. J. Roy. Meteor. Soc., 126 , 2353–2393.

    • Search Google Scholar
    • Export Citation

  • Shutts, G. J., 1995: Gravity-wave drag parametrization over complex terrain: The effect of critical-level absorption in directional wind-shear. Quart J. Roy. Meteor. Soc., 121 , 1005–1021.

    • Search Google Scholar
    • Export Citation

  • Shutts, G. J., 2003: Inertia-gravity wave and neutral Eady wave trains forced by directionally sheared flow over isolated hills. J. Atmos. Sci., 60 , 593–606.

    • Search Google Scholar
    • Export Citation

  • Shutts, G. J., and A. Gadian, 1999: Numerical simulations of orographic gravity waves in flows which back with height. Quart. J. Roy. Meteor. Soc., 125 , 2743–2765.

    • Search Google Scholar
    • Export Citation

  • Smith, R. B., 1979: Some aspects of the quasi-geostrophic flow over mountains. J. Atmos. Sci., 36 , 2385–2393.

  • Smith, R. B., 1984: A theory of lee cyclogenesis. J. Atmos. Sci., 41 , 1159–1168.

  • Smith, R. B., 1986: Further development of a theory of lee cyclogenesis. J. Atmos. Sci., 43 , 1582–1602.

  • Speranza, A., A. Buzzi, A. Trevisan, and P. Malguzzi, 1985: A theory of deep cyclogenesis in the lee of the Alps. Part I: Modifications of baroclinic instability by localized topography. J. Atmos. Sci., 42 , 1521–1535.

    • Search Google Scholar
    • Export Citation

  • Vadas, S. L., D. C. Fritts, and M. J. Alexander, 2003: Mechanism for the generation of secondary waves in wave breaking regions. J. Atmos. Sci., 60 , 194–214.

    • Search Google Scholar
    • Export Citation

  • Webster, S., A. R. Brown, D. R. Cameron, and C. P. Jones, 2003: Improvements to the representation of orography in the Met Office unified model. Quart. J. Roy. Meteor. Soc., 129 , 1989–2010.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 525 361 235
PDF Downloads 97 41 5