HR: 11:20h
AN: SA32A-05    [Abstracts]
TI: Analysis of High-Latitude Neutral Wind in the Lower Thermosphere: Comparison of Fall and Spring Equinoxes
AU: McCready, M
EM: mary.mccready@sri.com
AF: SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025, United States
AU: * Saotome, R
EM: Ryo.Saotome@trincoll.edu
AF: Trinity College, 300 Summit Street, Hartford, CT 06106, United States
AU: Goncharenko, L
EM: lpg@haystack.mit.edu
AF: Massachusetts Institute of Technology, Haystack Observatory, Off Route 40, Westford, MA 01886, United States
AU: Hagan, M
EM: hagan@ucar.edu
AF: National Center for Atmospheric Research, High Altitude Observatory, PO Box 3000, Boulder, Co 80309, United States
AB: Data obtained by the Sondrestrom incoherent scatter radar (67N, 309E) from campaigns during September 1-30, 2005 and March 6 - April 6, 2006 were analyzed to characterize neutral wind dynamics in the lower thermosphere at altitudes of 95-125 km. Lomb-Scargle spectral analysis revealed several significant waves in the data from both campaigns including 8-hour, semidiurnal and diurnal tides, as well as quasi 5-day and quasi-8 day planetary waves. Various harmonic components derived from the spectral analysis were then fit to the data over a range of altitudes in order to extract the amplitude and phase of the tidal components. During the spring equinox, a peak in the amplitude of the semi-diurnal tide is seen at around 110 km, in agreement with the Global Scale Wave Model. However, a peak seen in the diurnal tide for meridional equinox winds at 110 km is severely underestimated by the GSWM. For the meridional equinox winds in both the fall and spring, the amplitude of the semidiurnal tide is stronger than the diurnal component at altitudes below 105 km, while the opposite is shown to be true for higher altitudes. This is also in disagreement with the GSWM, which predicts a larger semi-diurnal component at all altitudes. Daily variations in the mean winds and amplitudes for both the diurnal and semi- diurnal components are also observed, especially in the semi-diurnal tide amplitudes near the spring equinox and the diurnal tide amplitudes in meridional equinox winds. The presence and phase progression of an 8-hour wave, also not predicted by theoretical models, is discussed as well.
DE: 3369 Thermospheric dynamics (0358)
DE: 3389 Tides and planetary waves
DE: 3394 Instruments and techniques
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting