Mountain Waves and Downslope Winds

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  Launch print version

  Launch full media version

  Launch Quiz

  Published on: 2004-01-07
  Estimated time to complete: 2.00 - 3.00 h
  Includes audio: yes

  Topic Area(s)

  Mountain Meteorology
  

  Description:

  Mountain waves form above and downwind of topographic barriers and frequently pose a serious hazard to mountain aviation because of strong-to-extreme turbulence. This foundation module describes the features of mountain waves and explores the conditions under which they form. Like other foundation modules in the Mesoscale Primer, this module starts with a forecast scenario and concludes with a final exam. Rich graphics, audio narration, and frequent interactions enhance the presentation.

  Objectives:

  After completing this module, the learner should be able to do the following things.
  
  With regard to the hazards, features, and climatology of mountain waves and downslope winds:

  
  
  • Identify at least 2 hazards associated with mountain wave activity
  
  
  • Recall at least 3 atmospheric and topographic requirements for a mountain wave system
  
  
  • Describe the major features of a mountain wave system
  
  
  • Recall when and where mountain waves and downslope winds occur
  
  
  • Recall the location of the following winds: Chinook, Santa Ana, Bora, and Foehn
  
  

  With regard to downslope winds:

  
  
  • Recall characteristics of downslope winds
  
  
  • Describe why downslope winds are warm
  
  

  With regard to the origin of mountain waves and downslope winds:

  
  
  • Describe why air displaced over a mountain range starts to oscillate
  
  
  • Recall the conditions that lead to topographically-blocked flow in terms of mountain height, wind speed, stability, and Froude number
  
  
  • Describe the effects of wind shear and inversions on mountain wave activity
  
  
  • Define critical level
  
  
  • Discriminate between a self-induced critical level and a mean-state critical level
  
  
  • Describe the different types of rotors and their associated atmospheric conditions
  
  
  • Identify which type of rotor is associated with more turbulence
  
  

  With regard to forecasting mountain waves and downslope winds:

  
  
  • Recall the 1.6 rule-of-thumb
  
  
  • Recall what NWP model resolution is required to accurately depict mountain waves
  
  
  • Describe how a model's vertical coordinate system affects its ability to forecast mountain waves
  
  
  • Describe how radiosondes and pilot reports (PIREPs) can help with short-range forecasting of mountain waves
  
  
  • Describe how satellite imagery can be used to detect mountain wave activity with or without either daylight or clouds
  
  

  Keywords

  mountain wave, downslope winds, waves, turbulence, wind storm, gravity wave, standing wave, cap cloud, lee wave, rotor cloud, rotor, lenticular cloud, vertically-propagating wave, jump region, trapped lee wave, downslope wind, wind storm, foehn, bora, stability, topography, buoyancy, oscillation, orographic wave, froude number, critical level, mountaintop inversion, wind shear, topography, NWP, numerical weather prediction, model, resolution, rawinsonde, radiosonde, satellite, clear slot, AVHRR, fog product, IR, MODIS, water vapor, pilot reports, PIREPS, GOES, jet streak, MSLP