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Neutral Winds in the Upper Atmosphere

Neutral Winds in the Upper Atmosphere. Qian Wu National Center for Atmospheric Research. Outline. Overview of the upper atmosphere. Ozone heating. Neutral wind tides (the strongest dynamic feature). Why do we need to understand upper atmospheric winds?

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Neutral Winds in the Upper Atmosphere

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  1. Neutral Winds in the Upper Atmosphere Qian Wu National Center for Atmospheric Research

  2. Outline • Overview of the upper atmosphere. • Ozone heating. • Neutral wind tides (the strongest dynamic feature). • Why do we need to understand upper atmospheric winds? • How do we measure upper atmospheric winds? • Observational results. • Satellite and Balloon borne instruments.

  3. Upper Atmosphere

  4. Temperature Profile

  5. Forbes, Comparative Aeronomy, 2002

  6. Hagan et al. Global Scale Wave Model (GSWM, March)

  7. Hagan et al. GSWM (March)

  8. Semidiurnal Tide in Meridional Winds Hagan et al. GSWM (June)

  9. Hagan et al. GSWM (June)

  10. Phase Comparison

  11. Coriolis Force Effect on Tidal Phase Velocity + Coriolis force Meridional Zonal + In the Northern Hemisphere In the Southern Hemisphere + Coriolis force - Velocity

  12. Dynamics Equations

  13. Tidal Wave Function

  14. Why do we need to know upper atmosphere neutral wind tide? • Tides are generated in the stratosphere and strongly affected by changes in that region such as: • Gravity wave activities, • Quasi-biennial oscillation (QBO) in the equatorial region • Sudden stratosphere warming in the high latitudes • Long term trends in tides may be linked with changes in the stratosphere. • Tides also have a great impact on the equatorial ionosphere through dynamo effect.

  15. Neutral Wind Measurement

  16. Airglow A view from Space Shuttle

  17. Airglow Emission Rates O 5577A O2 (0,1) 8650A 97 km Altitude (km) 86 km Na 5893 A OH 8920 A

  18. Thermosphere Airglow Emission Rates Altitude (km) O 6300 A

  19. Airglow Emission Sources at Night O 6300 Å red line O 5577 Å green line Electron impact Electron impact Collisional deactivation of N2 Dissociative recombination OH emission

  20. Fabry-Perot Interferometer (FPI)

  21. Etalon

  22. Fabry-Perot Fringe Pattern

  23. FPI Configuration • Major Components • Sky scanner • Filters & filter wheel • Etalon & chamber • Thermal & pressure control • Focusing lens • Detector • Computer system • Highlights • Computerized micrometer • Daily laser calibration • High degree automation • Michigan heritage • NCAR enhancement

  24. North OH Airglow Layer West Zenith East • 45 deg 87 km 174 km South FPI 174 km (a) (b) Instrument Operation

  25. FPI at Resolute

  26. FPI at Resolute

  27. Instrument Electronics

  28. FPI Operational Mode

  29. FPI Fringes Laser 8920 5577 6300

  30. Mesospheric Wind Semidiurnal Tide

  31. Lower Thermospheric Wind Semidiurnal tide

  32. TIMED Fact Sheet

  33. Limb-Scan Measurements Airglow layer

  34. The TIDI Instrument The TIMED Doppler Interferometer (TIDI) is a Fabry-Perot interferometer for measuring winds in the mesosphere and lower thermosphere. Primary measurement: Global neutral wind field, 60–120 km Primary emission observed: O21S (0-0) P9 Additional emissions observed: O21S (0-0) P15, O21S (0-1) P7, O(1S) “green line” Telescope Assembly Profiler

  35. TIDI Measurement Viewing Directions 4 1 3 2 9 minutes Satellite Travel direction 4 1 3 2

  36. TIDI Local Time Coverage Day 80 2002 Shifting 12 minutes per day in local time

  37. TIDI Coldside Wind Vectors

  38. TIDI Warmside Wind Vectors

  39. TIDI Observations

  40. Model Winds (GSWM) Oberheide and Hagan

  41. Stratosphere Balloon Borne Fabry-Perot Interferometer • Allow daytime observation of thermospheric winds due to low solar scatter background at high altitudes. • Inexpensive compared to satellite instrument.

  42. Summary • Upper atmospheric winds contain strong global scale waves (e.g. tides). • Tides are related to changes in the stratosphere and can affect the ionosphere. • Upper atmospheric winds are the key to a better understanding of the ionosphere. • There is a lack of observation upper atmospheric winds on a global scale. • I see a great opportunity for future balloon and satellite missions.

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