Editorial Type:
Article
Article Type:
Research Article

Simulations of Observed Lee Waves and Rotor Turbulence

Hálfdán Ágústsson Institute for Meteorological Research, and University of Iceland, and Icelandic Meteorological Office, Reykjavík, Iceland

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Haraldur Ólafsson University of Iceland, and Icelandic Meteorological Office, Reykjavík, Iceland, and Bergen School of Meteorology, Geophysical Institute, University of Bergen, Bergen, Norway

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Print Publication:
01 Feb 2014
DOI:
https://doi.org/10.1175/MWR-D-13-00212.1
Page(s):
832–849
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Abstract

On 18 November 2008 a commercial aircraft encountered severe turbulence while flying in westerly flow along the southeastern coast of Iceland and descending from 2500 m down to the ground for a safe landing. Numerical simulations at horizontal resolutions of 9, 3, and 1 km are compared to the available observations. The simulations reproduce the situation, with an observed severe downslope windstorm at the ground as well as associated amplified lee waves and a rotor aloft, while climate data indicate that all observed westerly windstorms in the region are of the same type and occur in a similarly structured atmosphere. Strong shear turbulence is simulated at the interface of the lee wave and the rotor, as well as inside the rotor. The lee waves and the turbulence patterns are not stationary and as the upstream vertical wind shear increases, the lee wave becomes less steep, but the turbulence increases temporarily while the rotor circulation breaks down. From a forecasting perspective, this event could have been foreseen quite accurately, but not with the NWP tools that were in use for aviation forecasts, as their resolution was simply not adequate for resolving hazardous features of flow in and above complex terrain on the scale of this event. This event underlines the urgency of delivering products from finescale simulations over complex terrain to pilots and forecasters. Such products need to be developed taking into account the transient nature of the flows and the hazards.

Corresponding author address: Hálfdán Ágústsson, Institute for Meteorological Research, Orkugarði, Grensásvegi 9, 108 Reykjavík, Iceland. E-mail: halfdana@gmail.com

Abstract

On 18 November 2008 a commercial aircraft encountered severe turbulence while flying in westerly flow along the southeastern coast of Iceland and descending from 2500 m down to the ground for a safe landing. Numerical simulations at horizontal resolutions of 9, 3, and 1 km are compared to the available observations. The simulations reproduce the situation, with an observed severe downslope windstorm at the ground as well as associated amplified lee waves and a rotor aloft, while climate data indicate that all observed westerly windstorms in the region are of the same type and occur in a similarly structured atmosphere. Strong shear turbulence is simulated at the interface of the lee wave and the rotor, as well as inside the rotor. The lee waves and the turbulence patterns are not stationary and as the upstream vertical wind shear increases, the lee wave becomes less steep, but the turbulence increases temporarily while the rotor circulation breaks down. From a forecasting perspective, this event could have been foreseen quite accurately, but not with the NWP tools that were in use for aviation forecasts, as their resolution was simply not adequate for resolving hazardous features of flow in and above complex terrain on the scale of this event. This event underlines the urgency of delivering products from finescale simulations over complex terrain to pilots and forecasters. Such products need to be developed taking into account the transient nature of the flows and the hazards.

Corresponding author address: Hálfdán Ágústsson, Institute for Meteorological Research, Orkugarði, Grensásvegi 9, 108 Reykjavík, Iceland. E-mail: halfdana@gmail.com
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  • Ágústsson, H., and H. Ólafsson, 2004: Mean gust factors in complex terrain. Meteor. Z., 13 (2), 149–155.

  • Ágústsson, H., and H. Ólafsson, 2007: Simulating a severe windstorm in complex terrain. Meteor. Z., 16 (1), 111–122.

  • Ágústsson, H., and H. Ólafsson, 2010: The bimodal downslope windstorms at Kvísker. Meteor. Atmos. Phys., 116, 27–42, doi:10.1007/s00703-010-0075-y.

    • Search Google Scholar
    • Export Citation

  • Bao, J.-W., S. A. Michelson, L. Kantha, and J. W. Brown, 2008: Implementation of a two-equation vertical turbulent mixing scheme in a mesoscale atmospheric model. NOAA Tech. Memo. OAR PSD-311, National Oceanic and Atmospheric Administration, 33 pp.

  • Deng, A., and D. R. Stauffer, 2006: On improving 4-km mesoscale model simulations. J. Appl. Meteor. Climatol., 45, 361–381.

  • Doyle, J. D., and D. R. Durran, 2002: The dynamics of mountain-wave induced rotors. J. Atmos. Sci., 59, 186–201.

  • Doyle, J. D., and D. R. Durran, 2004: Recent developments in the theory of atmospheric rotors. Bull. Amer. Meteor. Soc., 85, 337–342.

  • Doyle, J. D., and D. R. Durran, 2007: Rotor and subrotor dynamics in the lee of three-dimensional terrain. J. Atmos. Sci., 64, 4202–4221.

    • Search Google Scholar
    • Export Citation

  • Doyle, J. D., M. A. Shapiro, Q. Jiang, and D. L. Bartels, 2005: Large-amplitude mountain wave breaking over Greenland. J. Atmos. Sci., 62, 3106–3126.

    • Search Google Scholar
    • Export Citation

  • Doyle, J. D., V. Grubišić, W. O. J. Brown, S. F. J. D. Wekker, A. Dörnbrack, Q. Jiang, S. D. Mayor, and M. Weissmann, 2009: Observations and numerical simulations of subrotor vortices during T-REX. J. Atmos. Sci., 66, 1229–1249.

    • Search Google Scholar
    • Export Citation

  • Doyle, J. D., and Coauthors, 2011: An intercomparison of T-REX mountain-wave simulations and implications for mesoscale predictability. Mon. Wea. Rev., 139, 2811–2831.

    • Search Google Scholar
    • Export Citation

  • Durran, D. R., 1990: Mountain waves and downslope winds. Atmospheric Processes over Complex Terrain, Meteor. Monogr., No. 45, Amer. Meteor. Soc., 59–81.

  • Durran, D. R., 2003: Mountain waves and downslope winds. Encyclopedia of Atmospheric Sciences, J. R. Holton, J. Pyle, and J. A. Curry, Eds., Elsevier Science Ltd., 1161–1169.

  • Feltz, W. F., K. M. Bedka, J. A. Otkin, T. Greenwald, and S. A. Ackerman, 2009: Understanding satellite-observed mountain-wave signatures using high-resolution numerical model data. Wea. Forecasting, 24, 76–86.

    • Search Google Scholar
    • Export Citation

  • Gohm, A., G. J. Mayr, A. Fix, and A. Giez, 2008: On the onset of bora and the formation of rotors and jumps near a mountain gap. Quart. J. Roy. Meteor. Soc., 134 (630), 21–46.

    • Search Google Scholar
    • Export Citation

  • Grell, G. A., J. Dudhia, and D. R. Stauffer, 1994: A description of the fifth-generation Penn State/NCAR Mesoscale Model (MM5). Tech. Rep. NCAR/TN-398+STR, National Center for Atmospheric Research, 122 pp.

  • Grubišić, V., and J. M. Lewis, 2004: Sierra wave project revisited: 50 years later. Bull. Amer. Meteor. Soc., 85, 1127–1142.

  • Grubišić, V., and B. J. Billings, 2007: The intense lee-wave rotor event of Sierra rotors IOP 8. J. Atmos. Sci., 64, 4178–4201.

  • Grubišić, V., and M. Orlić, 2007: Early observations of rotor clouds by Andrija Mohorovičić. Bull. Amer. Meteor. Soc., 88, 693–700.

    • Search Google Scholar
    • Export Citation

  • Grubišić, V., and I. Stiperski, 2009: Lee-wave resonances over double bell-shaped obstacle. J. Atmos. Sci., 66, 1205–1228.

  • Grubišić, V., and Coauthors, 2008: The terrain-induced rotor experiment: A field campaign overview including observational highlights. Bull. Amer. Meteor. Soc., 89, 1513–1533.

    • Search Google Scholar
    • Export Citation

  • Hertenstein, R. F., and J. P. Kuettner, 2005: Rotor types associated with steep lee topography: Influence of the wind profile. Tellus, 57A, 117–135.

    • Search Google Scholar
    • Export Citation

  • Horvath, K., D. Koracin, R. Vellore, J. Jiang, and R. Belu, 2012: Sub-kilometer dynamical downscaling of near-surface winds in complex terrain using WRF and MM5 mesoscale models. J. Geophys. Res., 117, D11111, doi:10.1029/2012JD017432.

    • Search Google Scholar
    • Export Citation

  • Janjić, Z. I., 1994: The step-mountain eta coordinate model: Further development of the convection, viscous sublayer, and turbulent closure schemes. Mon. Wea. Rev., 122, 927–945.

    • Search Google Scholar
    • Export Citation

  • Janjić, Z. I., 2001: Nonsingular implementation of the Mellor–Yamada level 2. 5 scheme in the NCEP Meso model. Scientific Rep. Office Note 437, National Centers for Environmental Prediction, 61 pp.

  • Jiang, Q., J. D. Doyle, and R. B. Smith, 2006: Interaction between trapped waves and boundary layers. J. Atmos. Sci., 63, 617–633.

  • Küttner, J. P., 1938: Moazagotl und föhnwelle. Beitr. Phys. Atmos., 25, 79–114.

  • Lane, T. P., J. Doyle, R. Sharman, M. A. Shapiro, and C. Watson, 2009: Statistics and dynamics of aircraft encounters of turbulence over Greenland. Mon. Wea. Rev., 137, 2687–2702.

    • Search Google Scholar
    • Export Citation

  • Lilly, D. K., 1978: A severe downslope windstorm and aircraft turbulence event induced by a mountain wave. J. Atmos. Sci., 35, 59–77.

  • Mellor, G. L., and T. Yamada, 1982: Development of a turbulence closure model for geophysical fluid problems. Rev. Geophys. Space Phys., 20, 851–875.

    • Search Google Scholar
    • Export Citation

  • Nance, L. B., and D. R. Durran, 1997: A modeling study of nonstationary trapped mountain lee waves. Part I: Mean flow variability. J. Atmos. Sci., 54, 2275–2291.

    • Search Google Scholar
    • Export Citation

  • Nance, L. B., and D. R. Durran, 1998: A modeling study of nonstationary trapped mountain lee waves. Part II: Nonlinearity. J. Atmos. Sci., 55, 1429–1445.

    • Search Google Scholar
    • Export Citation

  • Ólafsson, H., and H. Ágústsson, 2007: The Freysnes downslope windstorm. Meteor. Z., 16 (1), 123–130.

  • Ólafsson, H., and H. Ágústsson, 2009: Gravity wave breaking in easterly flow over Greenland and associated low level barrier- and reverse tip-jets. Meteor. Atmos. Phys., 104 (3), 191–197.

    • Search Google Scholar
    • Export Citation

  • Ólafsson, H., N. Jónasson, and S. Karlsdóttir, 2006: Háupplausnarreikningar til almennrar spágerðar (HRAS), lokaskýrsla (high-resolution atmospheric simulations, final report). Tech. Rep. 06011, Veðurstofa Íslands, 26 pp. [Available online at http://www.vedur.is/um-vi/utgafa/greinargerdir/.]

  • Ólafsson, H., Ó. Rögnvaldsson, J. Reuder, H. Ágústsson, G. N. Petersen, H. Björnsson, T. Jónsson, and J. E. Kristjánsson, 2009: Monitoring the Atmospheric Boundary Layer in the Artic (MABLA): The Gufuskálar project. Proc. 30th Int. Conf. on Alpine Meteorology (ICAM), Rastatt, Germany, Deutscher Wetterdienst, Annalen der Meteorologien 44, 192–193. [Available online at http://www.pa.op.dlr.de/icam2009/extabs/.]

  • Reinecke, P. A., and D. R. Durran, 2009: Initial condition sensitivities and the predictability of downslope winds. J. Atmos. Sci., 66, 3401–3418.

    • Search Google Scholar
    • Export Citation

  • Renfrew, I. A., and Coauthors, 2008: The Greenland Flow Distortion Experiment. Bull. Amer. Meteor. Soc., 89, 1307–1324.

  • Rögnvaldsson, Ó., J.-W. Bao, and H. Ólafsson, 2007: Sensitivity simulations of orographic precipitation with MM5 and comparison with observations in Iceland during the Reykjanes Experiment. Meteor. Z., 16 (1), 87–98.

    • Search Google Scholar
    • Export Citation

  • Rögnvaldsson, Ó., H. Ágústsson, and H. Ólafsson, 2011a: Aflræn niðurkvörðun veðurs innan LOKS verkefnisin (Dynamical downscaling of weather within the LOKS-project). Tech. Rep., Reiknistofa í veðurfræði, 29 pp. [Available online at http://riv.is/pages/1287-greinar-og-skyrslur/.]

  • Rögnvaldsson, Ó., J.-W. Bao, H. Ágústsson, and H. Ólafsson, 2011b: Downslope windstorm in Iceland–WRF/MM5 model comparison. Atmos. Chem. Phys., 11 (1), 103–120, doi:10.5194/acp-11-103-2011.

    • Search Google Scholar
    • Export Citation

  • Scorer, R. S., 1949: Theory of waves in the lee of mountains. Quart. J. Roy. Meteor. Soc., 75 (323), 41–56.

  • Sheridan, P., and S. Vosper, 2012: High-resolution simulations of lee waves and downslope winds over the Sierra Nevada during T-REX IOP 6. J. Appl. Meteor. Climatol., 51, 1333–1352.

    • Search Google Scholar
    • Export Citation

  • Skamarock, W. C., and Coauthors, 2008: A description of the Advanced Research WRF version 3. Tech. Rep. NCAR/TN-475+STR, National Center for Atmospheric Research, 125 pp.

  • Smith, R. B., 1980: Linear theory of stratified flow past an isolated mountain. Tellus, 32, 348–364.

  • Smith, R. B., 1987: Aerial observations of the Yugoslavian Bora. J. Atmos. Sci., 44, 269–297.

  • Smith, C. M., and E. D. Skyllingstad, 2009: Investigation of upstream boundary layer influence on mountain wave breaking and lee wave rotors using a large eddy simulation. J. Atmos. Sci., 66, 3147–3164.

    • Search Google Scholar
    • Export Citation

  • Smith, C. M., and E. D. Skyllingstad, 2011: Effect of inversion height and surface heat flux on downslope windstorms. Mon. Wea. Rev., 139, 3750–3764.

    • Search Google Scholar
    • Export Citation

  • Smith, R. B., Q. Jiang, and J. D. Doyle, 2006: A theory of gravity wave absorption by a boundary layer. J. Atmos. Sci., 63, 774–781.

  • Stiperski, I., and V. Grubišić, 2011: Trapped lee wave interference in the presence of surface friction. J. Atmos. Sci., 68, 918–936.

    • Search Google Scholar
    • Export Citation

  • Teixeira, M. A. C., J. L. Argain, and P. M. A. Miranda, 2013: Drag produced by trapped lee waves and propagating mountain waves in a two-layer atmosphere. Quart. J. Roy. Meteor. Soc., 139B, 964–981.

    • Search Google Scholar
    • Export Citation

  • Valkonen, T., T. Vihma, S. Kirkwood, and M. M. Johansson, 2010: Fine-scale model simulation of gravity waves generated by Basen Nunatak in Antarctica. Tellus, 62A, 319–332.

    • Search Google Scholar
    • Export Citation

  • Vosper, S. B., 2004: Inversion effects of mountain lee waves. Quart. J. Roy. Meteor. Soc., 130, 1723–1748.

  • Wyngaard, J. C., 2004: Toward numerical modeling in the “terra incognita.” J. Atmos. Sci., 61, 1816–1826.

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