1. Global dynamics in the MLT region
Seminar talk
Olexandr Lednyts'kyy 1
1 Institute of Physics, Ernst-Moritz-Arndt University Greifswald, Greifswald, Germany
Atomic oxygen dynamics in the MLT region th May, 2014

2. circulation in the middle atmosphere 2. Dynamical processes
1. Energy balance
chemical processes
dynamical processes
circulation in the middle atmosphere
2. Dynamical processes
GW interaction
anomalies in temperatures and winds
coupling of temperatures and winds
transport
tides
3. Chemical processes
energy sources
energy sinks
4. Analysis
drivers in the atmosphere
coupling of chemical and dynamical processes
variations due to chemical and dynamical processes
anomalies and wavelets
References and acknowledgements
Contents

3. Thermal structure of the atmosphere
Ionization
UV absorption by O2
Chemical heating: odd-H, -O
IR radiative cooling by CO2
UV absorption by O3
Surface heating
Liljequist and Cehak, 1994
1.1. Energy balance, chemical processes

4. Chemical constituents of the atmosphere
Thermosphere
dominant molecules (O2, N2) decrease
simple molecules (NO, CO) increase
dominance of atoms increases
excited states prevail
reactions are slower due to low density
ions and ion reactions are dominant
Upper mesosphere
dominant molecules (O2, N2) are well mixed
troposheric molecules H2O, CO2, [NO], [CO]
and atoms (O, H) become important
energetics is governed by excited states (O2*)
decreasing density affects 3-body reactions
diurnal variations are driven photochemically
Stratosphere and lower mesosphere
larger molecules from troposphere brake down
density is sufficient for 3-body reactions
daytime maximum: O, Cl, H, OH, NO, etc.
catalytic NOx, ClOx, HOx cycles destroy ozone
Composition control in the MLT O
produced locally from O2 and O3
transported from thermosphere O3
produced from O+O2
destroyed during the daytime
H, OH, HO2:
produced during the day from H2O
Smith, 2001
Brasseur and Solomon, 2005
1.1. Energy balance, chemical processes

5. Gravity waves Gravitational force
Atmospheric waves
Lamb-waves
Acoustical waves
Pressure gradient force
Planetary waves
Coriolis force
Acoustical gravity waves
Mixed ROSSBY-gravity waves
Infrasound waves
Gravity waves Gravitational force
GW sources
flow over mountains
flow over convective cloud
instability around the jet stream
geostrophic adjustment
GW dissipation
GW can be filtered and dissipated by stratospheric wind system
upon critical layer interactions
when phase speed is approximately equal to background wind speed
Pichler, 1997
1.2. Energy balance, dynamical processes

6. Gravity waves Gravity waves amplitudes grow exponentially with height
become large and unstable in the reentry regime, “drag” impulse and energy:
generate turbulence (turbulent mixing) and deposit heat there (turbopause)
cause momentum deposition in regions of vertical wind shears
reach critical level absorption that generates the QBO analogously
amplify the tides (Hines’ GW parameterization)
The deposited momentum
produces a net meridional circulation
cause the mesopause anomaly in temperature
Mayr et al., 2011
1.2. Energy balance, dynamical processes

7. Net meridional circulation and temperature
Meriwether and Gerrard, 2004
1.3. Energy balance, circulation in the middle atmosphere

8. Generation and influence on tides and waves
Mayr et al., 2011
2.1. Dynamical processes, GW interaction

9. Zonal mean temperatures and winds
2002 – 2011
1992 – 1995
Smith, 2012
2.2. Dynamical processes, anomalies in temperatures and winds

10. T-gradient coupling with single reversal of zonal mean winds
Dec Jan Feb Mar Apr
Month of 2009 – 2010
ECMWF
MLS
Dec Jan Feb Mar
Month of 2008 – 2009
MLS
Straub et al., 2012
Manney et al., 2009
2.2. Dynamical processes, coupling of temperatures and winds

11. Diffusion and advection
Molecular diffusion
diffusive component reduces gradients
“advective” component transports species differentially
affects H, H2, CO2, temperature in mesopause
diffusion rates depend on temperature
Eddy diffusion
is caused by turbulence or by any unresolved dynamical scales
plays the key role in the vertical transport due to strong mixing ratio gradients
mixing ratios of species and potential temperature have same diffusion coefficient
very variable due to intermittent dynamics
Advective transport
time scale of variability increases with spatial scale
propagation of low frequency waves (planetary and gravity waves) is affected by zonal wind
period
variability
gravity waves
hours
hours-seasons
tides
days-seasons
planetary waves
days
weeks-seasons
mean circulation
seasons
years
Smith, 2001
2.3. Dynamical processes, transport

12. Migrating tides Migrating diurnal tide Migrating semidiurnal tide
2002 – 2011
Distribution of terms in the thermal budget
diffusion
advection by the mean circulation
direct solar O2* and O3* heating (loss through airglow)
chemical heating (loss through airglow)
infrared cooling
Smith, 2012
2.3. Dynamical processes, tides

13. Impact of composition on energetics
IR radiation responds to local T, but IR emissions are inefficient (cold mesopause)
For comparable momentum forcing in a warmer region need stronger T response
Absorption of solar radiation depends on composition
O2: nm (Lyman-, Schumann-Runge continuum, Schumann-Runge bands)
O3: nm (Hartley band)
Acceptors of the absorbed energy
breakage of chemical bonds
excitation of vibrational or rotational levels of original absorber or its products
conversion into heat
Brasseur and Solomon, 2005
3.1. Chemical processes, energy sources

14. Terrestrial nightglow in the MLT region
Remote sensing observing techniques • In-situ: Balloon payload, rockets • Ground-based: radar, lidar, passive optics (imager, FPI, spectrograph) • Satellite
Mesosphere / Lower Thermosphere is difficult to reach for sparse ground-based observations of nightglow:
McDade, 1998
3.2. Chemical processes, energy sinks

15. Drivers in the atmosphere
Photolysis energy
breaks chemical bonds giving products
that can be converted to heat
hours or days after and far away
from original absorption
Dependence: sun angle, solar flux, columns of absorbing gases
Reactions concerned
are temperature and density dependent
O + O3 → O2 + O2
* O + O + M → O2 + M
* O + OH → H + O2
* O + HO2 → OH + O2
* H + O2 + M → HO2 + M
* O + O2 + M → O3 + M
H + O3 → OH + O2
* reaction rate decreases with temperature
Energy conservation and composition
radiative flux affect photolysis
absorption change atomic / molecular energy levels
energetic particles can generate ionized or excited states
temperature affects reaction rates
Anthropogenic gases
increased CO2 → cooling
increased hydrocarbons → ozone loss
Dynamics impacts composition
winds advect species
winds and temperature control propagation and dissipation of waves
Smith, 2001
4.1. Analysis, drivers

16. Photochemical destabilization of gravity waves
Air parcel trajectory in propagating GW
Composition and density
cold
high O, total density low
warm
low O, total density higher
Midnight O3 and O profiles
GW unstable growth rate
solid: high eddy diffusion coefficient, no net vertical velocity
dashed: low eddy diffusion coefficient, upward net vertical velocity
Xu et al., 2001
4.2. Analysis, coupling of chemical and dynamical processes

17. GW and composition variations
The cross-section of GW growth rate as a function of wavelength at 86 km
GW growth rate is large
longer vertical wavelengths
shorter horizontal wavelengths
Photochemical destabilization is preferable
low temperature
low diffusion
sharp vertical gradients of O
long vertical, short horizontal wavelengths
Composition variability
regular diurnal, seasonal and interannual time scales
irregular variability due to forcing from above (energy) and below (waves)
Composition feedback
affects all scales of motion from mean circulation to individual GW
controls the conversation of energy to heat
Xu et al., 2001
4.3. Analysis, variations due to chemical and dynamical processes

18. Analysis of temperature profiles
Rauthe et al., 2006
4.4. Analysis, anomalies and wavelets

19. Thank You! References and acknowledgements References
[Brasseur and Solomon, 2005] Brasseur, G. P., Solomon, S., Aeronomy of the Middle Atmosphere: Chemistry and Physics of the Stratosphere and Mesosphere, Atmospheric and Oceanographic Sciences Library, 2005
[Liljequist and Cehak, 1994] Liljequist, G.H., Cehak, K., Allgemeine Meteorologie, 1994
[Manney et al., 2009] Manney, G. L., Schwartz, M. J., Krüger, K., Santee, M. L., Pawson, S., Lee, J. N., Daffer, W. H., Fuller, R. A., Livesey, N. J., Aura Microwave Limb Sounder observations of dynamics and transport during the record-breaking 2009 Arctic stratospheric major warming, Geophys. Res. Letters, 36(L12815), 1 - 5, 2009
[Mayr et al., 2011] Mayr, H. G., Mengel, J. G., Chan, K. L., Huang, F.T., Middle atmosphere dynamics with gravity wave interactions in the numerical spectral model: Tides and planetary waves, J. Atm. Sol.-Ter. Phys., 73, , 2011
[McDade, 1998] McDade, I. C., The photochemistry of the MLT oxygen airglow emissions and the expected influences of tidal perturbations, Adv. Spuce Res. Vol. 21 (6), , 1998
[Meriwether and Gerrard, 2004] Meriwether, J. W., Gerrard, A. J., Mesosphere inversion layers and stratosphere temperature enhancement, Rev. Geophys., 42(RG3003), , 2004
[Pichler, 1997] Pichler, H., Dynamik der Atmosphäre, Spektrum, 1997
[Rauthe et al., 2006] Rauthe, M., Gerding, M., Höffner, J., Lübken, F.-J., Lidar temperature measurements of gravity waves over Kühlungsborn (54N) from 1 to 105 km: A winter-summer comparison, J. Geophys. Res., 111(D24108), , 2006
[Smith, 2001] Smith, A. K., CEDAR, 2001
[Smith, 2012] Smith, A. K., Global Dynamics of the MLT, Surv. Geophys., 2012
[Straub et al., 2012] Straub, C., Tschanz, B., Hocke, K., Kämpfer, N., Smith, A. K., Transport of mesospheric H2O during and after the stratospheric sudden warming of January 2010: observation and simulation, Atmos. Chem. Phys., 12, , 2012
[Xu et al., 2001] Xu, J., Smith, A. K., Brasseur, G. P.,Conditions for the photochemical destabilization of gravity waves in the mesopause region, J. Atm. Sol.-Ter. Phys., 63, , 2001
Thank You!
References and acknowledgements