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 27th May, 2014

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

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

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

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

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

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

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

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

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

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

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

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: 100-205 nm (Lyman-, Schumann-Runge continuum, Schumann-Runge bands) O3: 242-310 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

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

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

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

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

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

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, 711 - 730, 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), 787 - 794, 1998 [Meriwether and Gerrard, 2004] Meriwether, J. W., Gerrard, A. J., Mesosphere inversion layers and stratosphere temperature enhancement, Rev. Geophys., 42(RG3003), 1 - 31, 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), 1 - 11, 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, 5413 - 5427, 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, 1821 - 1829, 2001 Thank You! References and acknowledgements