Mountain Waves entering the Stratosphere

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]

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.]

Microwave Limb Scanner Jiang et al Global pattern of Gravity Waves in the upper atmosphere

Frequency w > 1 m s -1 and Mean TKE> 2 m 2 s -2 COAMPS Climate (Doyle) Tropopause Wind

Dashed Line = North Leg Solid Line = South leg

Note shorter wavelength ~15km

Wave Energy Components

(times 1000) Each point is a leg

Threshold? Lemoore and Visalia soundings Each point is a flight

Each point is a leg

Computed from the product of theta and displacement perturbation

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

Wavelength 20 km 10km Vertical Velocity Spectrum

9km 11km 13km RF10

9km 11km 13km RF10 North South

9km 11km 13km RF4 North South

9km 11km 13km RF4 North South

Vandenberg Windspeed Profiles: Big Wave Events (RF4,5,10) [Note oscillations in the stratosphere]

Vandenberg Theta Profiles: Big Wave Events (RF 4,5, 10)

April 16, 2006 Scorer Parameter from quadratic fit

Conserved Variable Diagram for a racetrack Dashed line = North Leg Solid line = South Leg

Mechanical Bernoulli Function for compressible steady flow GPS altitude Minor contributor as the A/C tries to fly at constant pressure altitude

Dual Conserved Variable Plots (RF4; March 14, 2006; Ozone Mechanical Bernoulli* [using GPS altitude]

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)

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

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

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

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.

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 Crocco’s 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

(Smith, 1985)

Other aircraft profiles: Ozone Air density Water Vapor Each point is a racetrack

Each point is one racetrack

Aircraft Profiles: All Big Wave Events (RF4,5,10) Each point is a racetrack