Observations of High Frequency GWs observed in mesospheric airglow, and the implication to the GW imposed zonal stress and the residual circulation Gary R. Swenson1, Fabio Vargas1, Alan Liu2, Xian Lu3, Zhenhua Li3, Chester Gardner1 Electrical and Computer Engineering, University of Illinois, Urbana, IL, United States. Physical Sciences, Embry Riddle Aeronautical University, Daytona Beach, FL, United States. Atmospheric Sciences, University of Illinois, Urbana, IL, United States.
Introduction • The background atmosphere and meridional circulation • OH and mesospheric airglows, and altitude weighting functions, I’/I • Directional statistics, and methods [Globally, the meridional component is toward the summer pole, at OH emission altitudes] • Momentum flux, methods of determination from airglow • Freely propagating versus damped • Momentum flux, statistical summary from a Brazilian study • Summary
The Lower and Middle Atmosphere Pres (mbar) km 90 0.003 80 0.009 70 0.05 60 0.2 50 0.7 40 3 30 11 20 55 10 270 0 1013 Pole Pole (WINTER) (SUMMER) Equator Gravity Waves (boxes are areas of induced drag) Circulation Zonal Winds Zonal Temps Planetary Waves Created by A. J. Gerrard, 10/99, based heavily on M. R. Schoeberl’s depiction
Upper atmospherewith cold summer and warm winter polar mesosphere Atmosphere with Motion
Residual Meridional Circulation Northern Winter H.-L. Liu. (2007)
Quasi monochromatic gravity waves-ever present λx= 28 km Cg= 40 m/s Ci= 40 m/s 105- O(1S) 95- O2 λz= 28 km Height (km) OH σ~±10 km 85- 75- 0 10 20 30 40 Horizontal Distance (km)
Dispersion Relationship Wave domain plot, intrinsc phase speed vs horizontal wavelength, versus vertical wavelength
Airglow Layers Vargas et al. (2007)
GW StatisticsPropagation Direction Maui, HI Tang et al. (2005) CachoeiraPaulista, BR Vargas (2007), Phd Theses
Dissipation of GWs(Lidar) Freely Propagating Saturated Damped Fritts (1984)
Dissipation of AGWs (Airglow) OH O2 O(1S) SpatialSeries Cross-Spectra Amplitude wave amplitudedecreasing withaltitude Vargas et al. (2011), in preparation
Modeled MF Divergence Dissipating AGWs Vargas et al, (2007)
Measured Flux DivergenceDissipating AGWs (I’/I ≥ 1%) Southern Hemisphere Vargas (2007), Phd Theses
Summary • A globally distributed set of ground based observations has been analyzed for the winter and summer directions of wave propagation. • There is experimental evidence that wave forcing is globally significant and opposite to the summer-winter residual meridional flow, predominantly propagating toward the summer pole. • AGW stress acting against the meridional flow imposes a deceleration which biases the magnitude of the meridional circulation (underestimates).