Mountain Waves

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Mountain Waves entering the Stratosphere
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Mountain Waves entering the Stratosphere New
aircraft data analysis techniques from
T-Rex Ronald B. Smith, Bryan Woods Yale
University New Haven, Connecticut J. Jensen, W.
Cooper, J. D. Doyle, Q. Jiang, V.
Grubisic National Center for Atmospheric
Research, Boulder, CO Naval Research
Laboratory, Monterey, CA, Desert Research
Institute, Reno, NV Support from the National
Science Foundation
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Outline

• T-Rex Events (march/April 2006)
• Potential and Kinetic energy
• Sensitivity to Mountain Top Winds
• Wave spectra with altitude
• Wind and stability profiles
• Layering of Mechanical Bernoulli and Ozone
• Summary and future work
• Warning Beware of speculation. This project is
  only a few weeks old.

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Global pattern of Gravity Waves in the
upper atmosphere
Microwave Limb Scanner Jiang et al
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Frequency w gt 1 m s-1 and Mean TKEgt 2 m2 s-2
Tropopause
Wind
COAMPS Climate (Doyle)
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Dashed Line North Leg Solid Line South
leg
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Note shorter wavelength 15km
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Wave Energy Components
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Each point is a leg
(times 1000)
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Each point is a flight
Threshold?
Lemoore and Visalia soundings
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Each point is a leg
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Computed from the product of theta and
displacement perturbation
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Wave Energy Comparison

• Observation
• Vertical KE 40 J/m2
• Horizontal KE 400 J/m2
• Potential Energy 4000 J/m2 (stratosphere)
• Interpretation
• Wave energy concentrated in the stratosphere
• Observations not consistent with vertically
  propagating or trapped waves rooted in the
  troposphere
• Horizontal KE may be enhanced by Bernoulli
  layering

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Vertical Velocity Spectrum
Wavelength 20 km 10km
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RF10
9km 11km
13km
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RF10
North
South
9km 11km
13km
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RF4
North
South
9km 11km
13km
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RF4
North
South
9km 11km
13km
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Vandenberg Windspeed Profiles Big Wave
Events (RF4,5,10)
Note oscillations in the stratosphere
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Vandenberg Theta Profiles Big Wave Events (RF
4,5, 10)
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Scorer Parameter from quadratic fit
April 16, 2006
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Conserved Variable Diagram for a racetrack
Dashed line North Leg Solid line
South Leg
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Mechanical Bernoulli Function for compressible
steady flow
Minor contributor as the A/C tries to fly at
constant pressure altitude
GPS altitude
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Dual Conserved Variable Plots(RF4 March 14,
2006 Leg _at_41kft)Ozone
Mechanical Bernoulli
using GPS altitude
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Conclusions

• The new GV aircraft is effective in monitoring
  stratospheric gravity waves.
• March/April 2006 was an active period for storms
  hitting the Sierras
• 3 large gravity wave events out of 8 Track B
  flights
• Wave energy is concentrated in the stratosphere
• Typical wavelength there is 15km
• Wave location suggests Sierra causation
• 2-D and steadiness are imperfect and variable
• Wave amplitude very sensitive to mountain top
  winds
• Strong wave events have similar wind environments
  (with a stratospheric critical level)

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Linear Theory

• Criterion for linear waves is nearly satisfied

• Vertically propagating gravity waves should have
  KE PE at each level (equipartition)
• Trapped waves should have PE concentrated in the
  active stable layer

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Speculations on wave dynamics

• Waves are rooted in the stratosphere
• Wave energy distributions are not consistent with
  vertically propagating or conventional trapped
  waves.
• Potential energy is concentrated in the
  stratosphere
• Scorer parameter exceeds the wavenumber only in
  the stratosphere
• Generation mechanism unknown probably non-linear

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Free surface (Critical layer?) All the potential
energy is here.
UMT website
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Speculations on layering

• Vertical advection by waves allows diagnosis of
  ozone layering and dynamic Bernoulli Layering
• GPS altitude is required for Bernoulli function
  determination (new!)
• Bernoulli Layering correlates with ozone layering
  in the stratosphere
• Layering may represent isentropic interleaving of
  stratospheric air masses, prior to the wave
  encounter
• Bernoulli layering contributes a false signal to
  the horizontal wave kinetic energy.

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Future work

• Improve GV instrument calibrations
• Compute wave energy flux using GPS altitude
• Improved wave energy density computations
• Momentum fluxes
• Improved Bernoulli computations
• PV computations using Croccos theorem
• Analysis of soundings
• Compare observations with linear wave theories
• Test non-linear theories of wave regeneration,
  undular bores, and critical level reflection
  and/or decoupling
• Determine the role of the critical level

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(Smith, 1985)
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Other aircraft profiles Ozone Air density Water
Vapor
Each point is a racetrack
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Each point is one racetrack
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Aircraft Profiles All Big Wave Events (RF4,5,10)
Each point is a racetrack
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