Mountain Waves entering the Stratosphere

1. Mountain Waves entering the Stratosphere

2. 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]

3. 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.]

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

5. Frequency w > 1 m s-1 and Mean TKE> 2 m2 s-2 Tropopause Wind COAMPS Climate (Doyle)

10. Dashed Line = North Leg Solid Line = South leg

12. Note shorter wavelength ~15km

13. Wave Energy Components

14. Each point is a leg (times 1000)

15. Each point is a flight Threshold? Lemoore and Visalia soundings

16. Each point is a leg

17. Computed from the product of theta and displacement perturbation

19. 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

20. Vertical Velocity Spectrum Wavelength 20 km 10km

21. RF10 9km 11km 13km

22. RF10 North South 9km 11km 13km

23. RF4 North South 9km 11km 13km

24. RF4 North South 9km 11km 13km

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

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

27. Scorer Parameter from quadratic fit April 16, 2006

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

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

33. Dual Conserved Variable Plots(RF4; March 14, 2006; Leg @41kft)Ozone Mechanical Bernoulli* [using GPS altitude]

34. 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)

35. 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

36. 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

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

38. 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.

39. 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

41. (Smith, 1985)

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

43. Each point is one racetrack

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