Browsing by Author "Hall, Chris"

Now showing items 41-48 of 48

    • Spectral characteristics of spring arctic mesosphere dynamics. 

      Hall, Chris; Manson, A.H.; Meek, C.E. (Journal article; Tidsskriftartikkel, 1998)
      The spring of 1997 has represented a stable period of operation for the joint University of Tromsù / University of Saskatchewan MF radar, being between refurbishment and upgrades. We examine the horizontal winds from the February to June inclusive and also include estimates of energy dissipation rates derived from signal fading times and presented as upper limits on the turbulent energy ...

    • Testing the hypothesis of the influence of neutral turbulence on the deduction of ambipolar diffusivities from meteor trail expansion 

      Hall, Chris; Aso, T.; Tsutsumi, M.; Nozawa, S.; Manson, A.H.; Meek, C.E. (Journal article; Peer reviewed; Tidsskriftartikkel, 2005-03-30)
      Fading times of radar echoes from underdense meteor trails in the upper mesosphere/lower thermosphere are commonly used to determine ambipolar diffusivities and hence ambient temperature. Diffusivities are generally expected to increase exponentially with height through the region from which the meteor trail echoes are obtained, viz., typically 70-110km altitude for a ~30-MHz radar. In practice, ...

    • Tidal signatures in mesospheric turbulence 

      Nozawa, S.; Hall, Chris; Manson, A.H.; Meek, C.E. (Journal article; Peer reviewed; Tidsskriftartikkel, 2006)
      We search for the presence of tidal signatures in high latitude mesospheric turbulence as parameterized by turbulent energy dissipation rate estimated using a medium frequency radar, quantifying our findings with the aid of correlation analyses. A diurnal periodicity is not particularly evident during the winter and spring months but is a striking feature of the summer mesopause. While semidiurnal ...

    • Tropopause height at 78 degrees N 16 degrees E: average seasonal variation 2007-2010 

      Hall, Chris; Hansen, Georg Heinrich; Sigernes, F; Kuyeng, Karim (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by ...

    • Tropopause height at 78°N 16°E: average seasonal variation 2007-2010 

      Hall, Chris; Hansen, Georg; Sigernes, Fred; Kuyeng, Karim (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      We present a seasonal climatology of tropopause altitude for 78° N 16° E derived from observations 2007–2010 by the SOUSY VHF radar on Svalbard. The spring minimum occurs one month later than that of surface air temperature and instead coincides with the maximum in ozone column density. This confirms similar studies based on radiosonde measurements in the arctic and demonstrates downward control by ...

    • Vertical and interhemispheric links in the stratosphere-mesosphere as revealed by the day-to-day variability of Aura-MLS temperature data 

      Hall, Chris; Xu, X; Manson, A.H.; Meek, Chris; Chshyolkova, Tatyana; Drummond, J. R.; Riggin, D.; Hibbins, RE (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)

    • Winter warmings, tides and planetary waves. Comparisions between CMAM (with interactive chemistry) and MFR-MetO observations and data. 

      Manson, A.H.; Hall, Chris; Meek, C.; Chshyolkova, T.; McLandress, C.; Avery, S.K.; Fritts, D.C.; Hocking, W.K.; Igarashi, K.; MacDougall, J.W.; Murayama, Y.; Riggin, D.C.; Thorsen, D.; Vincent, R.A. (Journal article; Peer reviewed; Tidsskriftartikkel, 2006-10-20)
      Following earlier comparisons using the Canadian Middle Atmosphere Model (CMAM, without interactive chemistry), the dynamical characteristics of the model are assessed with interactive chemistry activated. Time-sequences of temperatures and winds at Tromsø (70° N) show that the model has more frequent and earlier stratospheric winter warmings than typically observed. Wavelets at mesospheric heights ...

    • Zonal Wave Number Diagnosis of Rossby Wave-Like Oscillations Using Paired Ground-Based Radars 

      He, Maosheng; Yamazaki, Yosuke; Hoffmann, Peter; Hall, Chris; Tsutsumi, Masaki; Li, Guozhu; Chau, Jorge L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-03)
      Free traveling Rossby wave normal modes (RNMs) are often investigated through large-scale space-time spectral analyses, which therefore is subject to observational availability, especially in the mesosphere. Ground-based mesospheric observations were broadly used to identify RNMs mostly according to the periods of RNMs without resolving their horizontal scales. The current study diagnoses zonal ...