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Mountain waves (Mountain-induced clouds)

Mountain waves (Mountain-induced clouds). Hydraulic jump or rotor clouds in the Owens Valley Looking south on east side of Sierras; photo by glider pilot Robert Symons. Lenticular clouds http://www.photolib.noaa.gov/historic/nws/wea00108.htm. Lenticular clouds over Lake Tahoe

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Mountain waves (Mountain-induced clouds)

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  1. Mountain waves(Mountain-induced clouds)

  2. Hydraulic jump or rotor clouds in the Owens Valley Looking south on east side of Sierras; photo by glider pilot Robert Symons

  3. Lenticular clouds http://www.photolib.noaa.gov/historic/nws/wea00108.htm

  4. Lenticular clouds over Lake Tahoe (photo by RGF)

  5. Lenticular clouds http://www.photolib.noaa.gov/historic/nws/wea00010.htm

  6. Lenticular/cap/banner clouds over Mt. Rainier http://www.phototripusa.com/images/rwarfield/rw_3843_12.html

  7. Lee waves forced by the Appalachians 13 April 2007

  8. Lee waves downwind of Rockies 17 March 2005

  9. Lee waves in Nevada 17 March 2005

  10. Lee waves on Mars http://www.solarviews.com/raw/mars/leewave.gif

  11. Background on gravity wavesand pendulum equations

  12. An oscillating parcel in a stable environment z’ = parcel vertical displacement N = Brunt-Vaisalla frequency Assumed solution: wavy in time… Result: where

  13. Environmental response to oscillating parcels Assumed solution wavy in time & space where

  14. Gravity wave frequency equation Still proportional to N Two waves - opposite directions Period shorter in more stable environment Horizontal phase speeds

  15. DTDM animation input_strfcn_isolated_nowind.txt

  16. Phase line tilt with height Westward wave tilts westward with height; Eastward wave tilts eastward Tilt implies vertical propagation

  17. Adding a mean flow (constant w/ height) Owing to mean flow, one wave speeds up, one slows down Mountain waves are horizontally stationary gravity waves

  18. Mountain wave analysis • Adiabatic, Boussinesq, inviscid • But linearize about a mean state with wind, as well as vertical shear and even curvature shear, so • Assume locally steady state

  19. Mountain wave equation l2 = Scorer parameter

  20. Cases to be examined • Sinusoidal terrain • l2 constant with height – flow with constant stability and mean wind • l2 variable with height • Isolated mountain • Conditions for wave trapping leading to lenticular clouds

  21. Sinusoidal mountain l2 < k2 Narrow mountain Waves decay w/ z l2 > k2 Wide mountain Waves preserved w/ z, mimic mountain shape

  22. Isolated ridge Narrow mountain wide mountain l2 > k2 l2 < k2

  23. More stable layer below - trapped lee waves & lenticular/lee wave clouds

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