Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Formation Mechanisms of the Mesoscale Environment Conducive to a Downslope Windstorm over the Cuyamaca Mountains Associated with Santa Ana Wind during the Cedar Fire (2003)

Formation Mechanisms of the Mesoscale Environment Conducive to a Downslope Windstorm over the... AbstractNumerical simulations were conducted to investigate the upstream environment’s impacts on the airflow over the lee slope of the Cuyamaca Mountains (CM) near San Diego, California, during the Cedar Fire that occurred from 25 to 29 October 2003. The upstream environment was largely controlled by a southwest–northeast-oriented upper-tropospheric jet streak that rotated around a positively tilted ridge within the polar jet stream. Three sequential dynamical processes were found to be responsible for modifying the mesoscale environment conducive to low-level momentum and dry air that sustained the Cedar Fire. First, the sinking motion associated with the indirect circulation of the jet streak’s exit region strengthened the midtropospheric flow over the southern Rockies and the lee slope of the Sawatch and San Juan Ranges, thus modestly affecting the airflow by enhancing the downslope wind over the CM. Second, consistent with the coupling process between the upper-level sinking motion, downward momentum transfer, and developing lower-layer mountain waves, a wave-induced critical level over the mountain produced wave breaking, which was characterized by a strong turbulent mixed region with a wind reversal on top of it. This critical level helped to produce severe downslope winds leading to the third stage: a hydraulic jump that subsequently enhanced the downstream extent of the strong winds conducive to the favorable lower-tropospheric environment for rapid fire spread. Consistent with these findings was the deep-layer resonance between the mountain surface and tropopause, which had a strong impact on strengthening the severe downslope winds over the lee slope of the CM accompanying the elevated strong easterly jet at low levels. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Applied Meteorology and Climatology American Meteorological Society

Formation Mechanisms of the Mesoscale Environment Conducive to a Downslope Windstorm over the Cuyamaca Mountains Associated with Santa Ana Wind during the Cedar Fire (2003)

Download PDF
22 pages

Loading next page...
 
/lp/american-meteorological-society/formation-mechanisms-of-the-mesoscale-environment-conducive-to-a-biC8jJ1K5i
Publisher
American Meteorological Society
Copyright
Copyright © American Meteorological Society
ISSN
1558-8432
eISSN
1558-8432
DOI
10.1175/jamc-d-22-0025.1
Publisher site
See Article on Publisher Site

Abstract

AbstractNumerical simulations were conducted to investigate the upstream environment’s impacts on the airflow over the lee slope of the Cuyamaca Mountains (CM) near San Diego, California, during the Cedar Fire that occurred from 25 to 29 October 2003. The upstream environment was largely controlled by a southwest–northeast-oriented upper-tropospheric jet streak that rotated around a positively tilted ridge within the polar jet stream. Three sequential dynamical processes were found to be responsible for modifying the mesoscale environment conducive to low-level momentum and dry air that sustained the Cedar Fire. First, the sinking motion associated with the indirect circulation of the jet streak’s exit region strengthened the midtropospheric flow over the southern Rockies and the lee slope of the Sawatch and San Juan Ranges, thus modestly affecting the airflow by enhancing the downslope wind over the CM. Second, consistent with the coupling process between the upper-level sinking motion, downward momentum transfer, and developing lower-layer mountain waves, a wave-induced critical level over the mountain produced wave breaking, which was characterized by a strong turbulent mixed region with a wind reversal on top of it. This critical level helped to produce severe downslope winds leading to the third stage: a hydraulic jump that subsequently enhanced the downstream extent of the strong winds conducive to the favorable lower-tropospheric environment for rapid fire spread. Consistent with these findings was the deep-layer resonance between the mountain surface and tropopause, which had a strong impact on strengthening the severe downslope winds over the lee slope of the CM accompanying the elevated strong easterly jet at low levels.

Journal

Journal of Applied Meteorology and Climatology – American Meteorological Society

Published: Nov 7, 2022

References

  • Cedar Fire incident information
  • Top 20 largest California wildfires
  • Downslope windstorms of San Diego County. Part I: A case study
    Cao, Y.; Fovell, R. G.
  • Climatology of storm reports relative to upper-level jet streaks
    Clark, A. J.; Schaffer, C. J.; Gallus, W. A.; Johnson-O’Mara, K.
  • On the evolution and stability of finite-amplitude mountain waves
    Clark, T. L.; Peltier, W. R.
  • Critical level reflection and the resonant growth of nonlinear mountain waves
    Clark, T. L.; Peltier, W. R.
  • Large-amplitude mountain wave breaking over Greenland
    Doyle, J. D.; Shapiro, M. A.; Jiang, Q.; Bartels, D. L.
  • An intercomparison of T-REX mountain-wave simulations and implications for mesoscale predictability
    Doyle, J. D.
  • Mountain waves and downslope winds
    Durran, D. R.; Banta, R. M.
  • Another look at downslope winds. Part II: Nonlinear amplification beneath wave-overturning layers
    Durran, D. R.; Klemp, J. B.
  • ERA5 reanalysis (0.25° latitude-longitude grid)
  • Glossary of Meteorology
    Glickman, T. S.
  • Synoptic-scale and mesoscale environments conducive to forest fires during the October 2003 extreme fire event in Southern California
    Huang, C.; Lin, Y. L.; Kaplan, M. L.; Charney, J. J.
  • Radiative forcing by long-lived greenhouse gases: Calculations with the AER radiative transfer models
    Iacono, M. J.; Delamere, J. S.; Mlawer, E. J.; Shephard, M. W.; Clough, S. A.; Collins, W. D.
  • A numerical study on severe downslope windstorms occurred on 5 April 2005 at Gangneung and Yangyang, Korea
    Jang, W.; Chun, H.-Y.
  • The step-mountain eta coordinate model: Further developments of the convection, viscous sublayer, and turbulence closure schemes
    Janjić, Z. I.
  • Southern California wildfires October 20 to November 3, 2003
    Johnson, D. L.
  • The Kain–Fritsch convective parameterization: An update
    Kain, J. S.
  • A study of track deflection associated with the landfall of Tropical Cyclone Sidr (2007) over the Bay of Bengal and Bangladesh
    Karim, S. M. S.; Lin, Y.-L.
  • The dynamics of wave-induced downslope winds
    Klemp, J. B.; Lilly, D. R.
  • Flow regimes and transient dynamics of two-dimensional stratified flow over an isolated mountain ridge
    Lin, Y.-L.; Wang, T.-A.
  • Bulk parameterization of the snowfield in a cloud model
    Lin, Y.-L.; Fairly, R. D.; Orville, H. D.
  • Some aspects of the flow of stratified fluids: Part I. A theoretical investigation
    Long, R. R.
  • A new theory for downslope windstorms and trapped mountain waves
    Lott, F.
  • Radiative transfer for inhomogeneous atmospheres: RRTM, a validated correlated-k model for the longwave
    Mlawer, E. J.; Taubman, S. J.; Brown, P. D.; Iacono, M. J.; Clough, S. A.
  • Basic laws of turbulent mixing in the surface layer of the atmosphere
    Monin, A. S.; Obukhov, A. M.
  • NCEP FNL operational model global tropospheric analyses, continuing from July 1999
  • The evolution and stability of finite-amplitude mountain waves. Part II: Surface wave drag and severe downslope windstorms
    Peltier, W. R.; Clark, T. L.
  • Santa Ana winds: A descriptive climatology
    Rolinski, T.; Capps, S. B.; Zhuang, W.
  • The instability of long’s stationary solution and the evolution toward severe downslope windstorm flow. Part I: Nested grid numerical simulations
    Scinocca, J. F.; Peltier, W. R.
  • A description of the Advanced Research WRF Model version 4
    Skamarock, W. C.
  • Santa Ana winds and the fire outbreak of fall 1993
    Small, I. J.
  • The influence of mountains on the atmosphere
    Smith, R. B.
  • On severe downslope winds
    Smith, R. B.
  • LFM forecast variables related to Santa Ana wind occurrences
    Sommers, W. T.
  • NOAA’s HYSPLIT atmospheric transport and dispersion modeling system
    Stein, A. F.; Draxler, R. R.; Rolph, G. D.; Stunder, B. J. B.; Cohen, M. D.; Ngan, F.
  • A one-dimensional time-dependent cloud model
    Sun, W.-Y.; Chen, S.-H.
  • Implementation and verification of the unified Noah land-surface model in the WRF model
    Tewari, M.
  • Wave ducting in a stratified shear flow over a two-dimensional mountain. Part II: Implications for the development of high-drag states for severe downslope windstorms
    Wang, T.-A.; Lin, Y.-L.