Atmospheric coupling by gravity waves, tides, and

planetary waves

L. Goncharenko,

MIT Haystack Observatory

HEPPA/SOLARIS2012, October 10, 2012 1

2

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