Observations of Mesospheric Gravity Waves and Winds

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Observations of Mesospheric Gravity Waves and
Winds

• Qian Wu
• High Altitude Observatory

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Overview

• MLT observational projects at HAO
• All sky camera (gravity wave monitoring)
• Fabry-Perot Interferometer (mesosphere neutral
  wind)
• Gravity wave observation at mid-latitudes
  (seasonal variation)
• Examples of possible gravity wave and neutral
  wind interaction at high latitudes
• Summary

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All Sky Camera Observation
93-96 Peach Mountain Michigan (40 N) 96-05
Resolute, Canada (75 N)
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FPI Obsrevations
9398 Peach Mountain, Michigan (40 N) 95-05
Resolute, Canada (75 N)
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FPI Measurements in MLT region
Wavelength Emitter Altitude Range 8920 Å
OH 87 km 5577 Å O 97 km
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Gravity Wave at Peach Mountain (40 N)
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Seasonal Variation of GW Occurrence at
Mid-latitude (40 N)
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Day 95359 Neutral Winds

• North
• South
• East
• West
• Zero
• Data coverage

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Day 95359 Event

• Strong 12-hour wave in the neutral winds.
• Strong eastward and southward background winds.
• Gravity waves propagating mostly in the
  west-northwest direction.

Black arrow GW travel direction White line
neutral wind vector
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Day 95359 Event

• Strong 12-hour wave in the neutral winds.
• Strong eastward and southward background winds.
• Gravity waves propagating mostly in the
  west-northwest direction.

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Day 97353 Neutral Winds

• North
• South
• East
• West
• Zero
• Data coverage

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Day 97353 Event

• 12-hour wave in the meridional winds.
• Northward background wind.

• Near zero zonal background wind.
• Gravity waves propagating westward and eastward
  according to the neutral wind change.

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Day 97353 Event

• 12-hour wave in the neutral winds.
• northward background wind.

• Near zero zonal background wind.
• Gravity waves propagating westward and eastward
  according to the neutral wind change.

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Day 97354 Neutral Winds

• North
• South
• East
• West
• Zero
• Data coverage

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Day 97354 Event

• Strong 12-hour wave in the neutral winds.
• Strong northward and westward background winds.
• Gravity waves propagating mostly eastward.

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Day 97354 Event

• Strong 12-hour wave in the neutral winds.
• Strong northward and westward background winds.
• Gravity waves propagating mostly eastward.

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Day 98000 Neutral Winds

• North
• South
• East
• West
• Zero
• Data coverage

• All sky camera coverage

Gravity wave propagating westward
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Day 98000 Event

• Strong oscillation with a period close to 8 hours
  in the neutral winds.
• Near zero meridional background wind and strong
  eastward zonal background wind.
• Gravity waves propagating mostly westward with
  both northward and southward tendencies.

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Day 98000 Event

• Strong oscillation with a period close to 8 hours
  in the neutral winds.
• Near zero meridional background wind and strong
  eastward zonal background wind.
• Gravity waves propagating mostly westward with
  both northward and southward tendencies.

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Summary

• At mid-latitude gravity wave occurrence shows
  strong seasonal variation and the waves were
  anisotropic.
• The wave propagation direction and neutral wind
  direction tend to be opposite of each other
  probably because of the filtering effect.
• If the neutral wind is weak, it seems to have
  less effect on the gravity wave.
• Interaction between the gravity wave and neutral
  wind is complex.