HR: 13:30h
AN: SA53A-01    [Abstracts]
TI: Comparative Study of Short Term Tidal Variability
AU: * Liu, H
EM: liuh@ucar.edu
AF: High Altitude Observatory, National Center for Atmospheric Research, POBox 3000, Boulder, CO 80307-3000 United States
AU: Li, T
EM: taoli@lamar.colostate.edu
AF: Physics Department,, Colorado State University, Fort Collins, CO 80523 United States
AU: She, C
EM: joeshe@lamar.colostate.edu
AF: Physics Department,, Colorado State University, Fort Collins, CO 80523 United States
AU: Oberheide, J
EM: joberh@uni-wuppertal.de
AF: Physics Department, University of Wuppertal, Gauss-Str. 20, Wuppertal, D-42097 Germany
AU: Wu, Q
EM: qwu@ucar.edu
AF: High Altitude Observatory, National Center for Atmospheric Research, POBox 3000, Boulder, CO 80307-3000 United States
AU: Hagan, M E
EM: hagan@ucar.edu
AF: High Altitude Observatory, National Center for Atmospheric Research, POBox 3000, Boulder, CO 80307-3000 United States
AU: Roble, R G
EM: roble@ucar.edu
AF: High Altitude Observatory, National Center for Atmospheric Research, POBox 3000, Boulder, CO 80307-3000 United States
AB: The wind and temperature measurements from an unusually long period operation of the sodium lidar at Colorado State University (41N, 105W) around September equinox 2003 shows significant short term tidal variability (She et al, 2004). Coincident with the large tidal changes, a strong temperature inversion layer was also observed above 90 km. Examination of the SABER temperature at the same time not only confirms the existence of the inversion layer but also reveals the global nature of the inversion. It thus suggests the presence of a planetary wave in the mesosphere, according to Sassi et al (2002). Because the strong inversion was only observed for a few days, the planetary wave was probably a transient wave, consistent with previous studies of planetary waves around equinox (Taylor et al., 2001, Liu et al., 2001). The large tidal variability, therefore, is probably a consequence of the interaction between the transient planetary wave and the tides. This possibility is investigated using the NCAR thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) and comparing model results with the lidar, SABER, and TIDI measurements. With a large transient planetary wave specified at the model lower boundary, the model is able to produce strong tidal variability comparable to that from the lidar observation. Temperature inversion due to planetary wave decaying is similar to that from the SABER measurement. Model results also show that non-migrating tides are generated by the planetary wave/tidal interaction, as noted in Hagan and Roble (2001). The latitudinal structure of the migrating diurnal tide also changes quite significantly as a result of the interaction, suggesting excitation of higher gravitational modes and/or rotational modes.
DE: 3332 Mesospheric dynamics
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3337 Numerical modeling and data assimilation
DE: 3384 Waves and tides
SC: SPA-Aeronomy [SA]
MN: 2005 Joint Assembly