Atmospheric coupling by gravity waves, tides, and ... · Atmospheric coupling by gravity waves,...
Transcript of Atmospheric coupling by gravity waves, tides, and ... · Atmospheric coupling by gravity waves,...
Atmospheric coupling by gravity waves, tides, and
planetary waves
L. Goncharenko,
MIT Haystack Observatory
HEPPA/SOLARIS2012, October 10, 2012 1
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CEDAR 2007 Student Workshop, June 20072
ITM System
0 km
60 km
500 km
Pole Equator
Mass Transport
Wave
Generation
Planetary Waves
Convective
Generation
of Gravity
Waves & Tides
Turbulence
CO2
CH4
CO2 Cooling
Ion Outflow
Solar Heating
The ITM SystemThe ITM System H
Escape
Wind Dynamo
BEEnergetic
ParticlesB
Polar/Auroral
Dynamics
E
Magnetospheric
Coupling
Joule Heating
H2O
solar-driven tides
O3NOTopographic
Generation
of Gravity
Waves
Controlled experiment is not an option…
Waves in the atmosphere
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Planetary waves Period: 2-16 days
Tides Period: 24-h, 12-h, 8-h
Migrating Non-migrating
Gravity waves Period: minutes to
hours
Wave dynamics • Atmospheric waves are a main coupling process in the atmosphere
– By conveying momentum from lower altitudes [source] to high altitudes [sink] waves link different altitude regimes in Earth's atmosphere (troposphere, stratosphere, mesosphere, thermosphere)
• Wave sources are mostly located in the troposphere and tropopause
• Waves are excited by many different sources - convection, weather systems, geostrophic adjustment, and orographic forcing
• Waves propagate vertically to less dense regions; wave amplitudes exponentially increase with height
– From ~1K in the troposphere to ~100K in the thermosphere
• Momentum is deposited where the waves break
– Wave breaking drives the atmospheric residual circulation (Brewer-Dobson circulation
– Wave breaking drives the vertical temperature structure of the atmosphere (e.g. cold summer mesopause) 4
Dynamics in the mesosphere- lower thermosphere
Tidal Variability• Gravity Wave Interactions :
• Planetary Wave Interactions
She et al., 2003
Results obtained for a 9 day run by the CSU UVT lidar illustrate the variability of
the tidal structure in response to GW and tidal fluctuations.
• Atmospheric tides dominate the dynamics in MLT region
• Short-term tidal variability due to tide-gravity wave and/or tide – planetary wave interactions
• Combined influences of tides and PW can drive fast transport in the MLT
She, 2004, CSU lidar data Yue and Liu, 2011, TIMEGCM simulations
Atmospheric gravity waves • Gravity waves are buoyancy waves • Frequencies greater than N (Brunt-Vaisala) and less than f (Coriolis
parameter); period – 5 mins to ~1 day • Typical vertical wavelength in the mesosphere: 2-3 km to 30 km • Horizontal wavelengths: tens to thousands km • GW sources:
– Topography • Flow over a mountain range • Mainly northern hemisphere winter
– Convection • Flow over a moving mountain • Common in tropics and summertime extratropics
– Jet instability • Mostly in the winter hemisphere • More prevalent in the northern hemisphere
– Other • Shear generation, geostrophic adjustment, wave-wave interaction, secondary wave
generation from wave breaking regions
• Global circulation models use GW parameterization schemes to include GW transfer of momentum – major source of controversy
Maps of gravity wave properties
Alexander et al., 2008
Temperature amplitude
Momentum flux
Vertical wavelength
Horizontal wave number
• Longitudinal asymmetry • Hemispheric asymmetry – seasonal dependence
HIRDLS, May 2006, 20-30km
GW propagation: Filtering by a wind system
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Change of Gravity Wave Forcing between summer and winter
• Filtering of gravity waves by stratospheric wind system: gravity wave will be
reflected or absorbed at critical layer.
– Eastward stratospheric jet under normal winter conditions: dominant westward
propagating gravity waves in the mesosphere.
– Stratospheric wind reversal during equinox: dominant direction of gravity wave in
mesosphere also reverses due to filtering.
winter summer
• GW are reflected or absorbed at the critical layer • Winter: eastward stratospheric wind leads to dominant westward propagating GW • Summer: westward stratospheric wind leads to dominant eastward propagating GW
Yigit and Medvedev, 2009
GW effects in the upper thermosphere
• Heating or cooling by breaking or dissipating GW extends to the upper thermosphere • Net effect of GW is cooling due to downward heat flux • Cooling up to ~150-200 K/day; higher at high latitudes • GW significantly contribute to the thermal balance of the thermosphere
Gravity wave effects in the ionosphere
Data: digisonde, Fortaleza, Brazil Model: TIMEGCM
~8% in TEC, Vadas and Liu, 2009
Data: PFISR, Alaska
40% variation in Ne, ~1.5h, Fritts et al., 2008
20% in Ne, ~20mins, Vadas and Nicolls, 2009 10
Reviews: Fritts and Alexander, 2003, Fritts and Lund, 2011
GW can produce secondary GW and TID Propagates globally (Gardner and Schunk, 2011)
Tides • Solar tides
– Excited through periodic absorption of solar radiation – Periods – harmonics of a solar day
• Diurnal - 24-h, H2O • Semidiurnal – 12-h, O3
• Terdiurnal – 8-h
– Migrating tides • Propagate westward with Sun
– Nonmigrating tides • Generated by longitudinal asymmetries in absorbing media or
by interaction of planetary waves with migrating tides • Propagate eastward, westward, or stand • Produce longitudinal variations in parameters
• Lunar tides – Gravitational forcing; 12-h tide is the strongest
CEDAR 2007 Student Workshop, June 200725
Solar Thermal Tides
Solar thermal tides are excited in a planetary atmosphere
through the periodic (local time, longitude) absorption of
solar radiation.
In general, tides are capable of propagating vertically to
higher, less dense, regions of the atmosphere; the
oscillations grow exponentially with height.
The tides are dissipated by molecular diffusion above 100
km, their exponential growth with height ceases, and they
deposit mean momentum and energy into the
thermosphere.
GSWM migrating diurnal tide, April
Maura Hagan CEDAR Prize Lecture June 28, 2004
� ~60 m/s peak near+/-30o & 105 km
� Symmetric phase{� > 75 m/s peak near
+/-20o & 105 km
� Asymmetric phase{� > 15 cm/s peak
near 0o & 100 km� Symmetric phase{� > 25oK peak
near 0o & 115 km
� Symmetric phase{
Zonal wind: Peaks at 60 m/s near +/-30o and 105 km
Meridional wind: Peaks at ~75 m/s near +/-20o and 105 km
Vertical wind: Peaks at~ 15 cm/s near 0o and 100 km
Temperature: Peaks at >25K near 0o and 115 km
Courtesy Maura Hagan
GSWM migrating semidiurnal tide, April
Maura Hagan CEDAR Prize Lecture June 28, 2004
Peaks comparatively higher than the diurnal tide
Comparatively stronger responses at mid-high latitudes
Comparatively weaker responses in the mesosphere
Comparatively longer vertical wavelength
No pronounced hemispheric phase asymmetry
• Peaks higher than diurnal tide, ~112-120 km
• Stronger responses at middle to high latitudes
• Comparatively weak in the mesosphere
• Comparatively longer vertical wavelength
• No pronounced hemispheric phase asymmetry
Courtesy Maura Hagan
GSWM diurnal zonal wind
Maura Hagan CEDAR Prize Lecture June 28, 2004
GSWM Diurnal Zonal Wind - 98 km
GSWM-00 migrating
tide
GSWM-00 +
latent heat response
• Multiple tidal modes are excited with different amplitude and vertical wavelength • Interaction can be constructive or destructive Courtesy Maura Hagan
Longitudinal variations in upper atmospheric parameters
• WN4 interpreted as modulation by DE3 (diurnal eastward) non-migrating tide; WN3 as DE2 (diurnal eastward) tide
• Variations reach 20-50% • Active research topic since 2006
4-peak (WN4) and 3-peak (WN3) longitudinal structures in: • F-region airglow (Sagawa, 2005,
England, 2006) • electron density (Lin, 2007,
Pedatella, 2008), • drifts (Hartman and Heelis, 2007,
Ren, 2009) • winds (Hausler, 2007) • temperature (Forbes, 2009)
Kil et al., 2008
15 Reviews: Kil and Paxton, 2011; England, 2011
Data: ROCSAT-1
Planetary (Rossby) waves
• Seen as oscillations in different parameters (temperature, wind) with multi-day periods
• Most common are 2, 5-6, 10, 16 day periods – Can be forced by longitudinally dependent heating
(land-sea contrast) or flow over topography
– Usually have small amplitudes
• Of particular importance are stationary planetary waves forced by flow over Rocky Mountains and Himalayas – Reach high amplitudes
– Play important role in sudden stratospheric warmings
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Propagation path of planetary waves
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Energy source
Polar wave guide
Equatorial wave guide
• Vertical propagation of planetary waves is only possible in westerly wind regime (winter conditions)
• Wind speed should be below some upper limit
• Two waveguides can be formed: polar wave guide and equatorial wave guide
• These wave guides provide ducting channel; planetary waves can penetrate though these channels to the stratosphere or mesosphere
• Planetary disturbances are absorbed along zero-wind lines
Stratospheric parameters during sudden stratospheric warming
Before SSW
SSW
Image credit: NASA Ozone Watch
EQUATOR
W
E
WARMING
WARMING
COOLING
POLE
mesosphere
stratosphere
troposphere
Coupling mechanism (Matsuno, 1971, Plumb, 1986, Garcia, 1987)
Planetary wave forcing drives a global circulation with a clockwise lower cell (<40km) and a counterclockwise upper cell (>40km)
COOLING
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Mesospheric effects of SSW • cooling of the polar mesosphere
(Labitzke 1972, 1981, Walterscheid 2000, Azeem 2005), changes in gravity waves, zonal mean flow, PW, tides (Hoffmann 2007, Yamashita 2010)
• Complex variations at middle and low latitudes (Pancheva 2008, Shepherd 2007, Sridharan and Sathiskumar, 2008, Lima 2011)
• Mesospheric anomalies preceed stratospheric anomalies
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Siskind et al., 2010
Yuan et al., 2012 Fort Collins lidar
Development of SSW anomalies
21 Limpasuvan et al., 2004
• Several stages of SSW with regards to the central day: • Onset (days -37 to -23) • Growth (days -22 to -8) • Maturity (days -7 to 7) • Decline (days 8 to 22) • Decay (days 24 to 37)
• During growth and mature stages, anomalies descend to the lower stratosphere
• Wind and temperature peaks in the mature stage; anomalously low PW begins
Mature stage is ~2 weeks; significant anomalies +/-40 days from the central date
NOx descend during winters with SSW
• NOx is strongly increased during winters with long-lasting SSW; up to a factor of 50 • Very low EPP in 2006 and 2009 • Dynamic conditions can strongly affect EPP impact on the middle atmosphere
Randall et al., 2009
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Ionospheric response to SSW: Temperature “sandwich”
•Data: warming at 120-140km; cooling above ~150 km; 12-hour wave;
•First experimental evidence of alternating warming and cooling of upper atmosphere
•Model: mesospheric cooling and secondary lower thermospheric warming
Goncharenko and Zhang, 2008
Data: Millstone Hill ISR, 42oN Model: TIMEGCM
Liu and Roble, 2002
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Upper atmospheric effects of SSW at low latitudes
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15 UT 21 UT
Entire daytime low to mid-latitude ionosphere is affected during stratwarming; Total Electron Content change 50-150%
Goncharenko et al., 2010
Chau et al., 2009
•Vertical plasma motion at ~250km: upward in the morning, downward in the afternoon -12-h wave
•Interpreted as evidence of enhanced 12-tide & E-region dynamo
Ozone variations in the low-latitude stratosphere during SSW
• Increase in the zonal mean ozone mass mixing ratio due to cooling and vertical transport
• Implications: amplified 12-h migrating tide
• Longitudinal distribution of ozone becomes strongly asymmetric
• Implications: amplified semiduirnal non-migrating tide of stratospheric origin
Goncharenko et al., 2012
Summary • Atmospheric waves are ubiquitous and persistent feature of the
Earth’s atmosphere • Gravity waves, tides, and planetary waves provide major
contributions to atmospheric circulation, structure, and variability • Transport of trace species is strongly affected • Strong evidence of significant upper atmospheric variability due to
the coupling with lower atmosphere • Variations in ionospheric parameters of the order of tens of percent
from each of different types of waves: – Up to 20-40% from gravity waves – Up to 20-50% due to non-migrating tides – Up to 40% from planetary waves – Up to a factor of 3-4 during stratwarmings
• Waves affect middle and upper atmosphere in multiple direct and indirect ways; most of them are not understood
• Better understanding of connection paths might hold a key to multiple unresolved problems in the middle and upper atmosphere
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Wave pattern over a two-dimensional ridge
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Calculated wave patterns over a two-dimensional ridge
Gaussian-shaped ridge, width 1 km Gaussian-shaped ridge, width 100 km
From Carmen J. Nappo, Atmospheric Gravity Waves, Academic Press