EGU21-15631
https://doi.org/10.5194/egusphere-egu21-15631
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Winds and tides of the Antarctic mesosphere and lower thermosphere: One year of meteor-radar observations over Rothera (68°S, 68°W) and comparisons with WACCM and eCMAM

Shaun M Dempsey1,2, Neil Hindley1, Tracy Moffat-Griffin2, Corwin Wright1, Anne Smith3, Jian Du4, and Nicholas Mitchell1,2
Shaun M Dempsey et al.
  • 1University of Bath, Bath, UK (smd62@bath.ac.uk)
  • 2British Antarctic Survey, Cambridge, UK
  • 3Atmospheric Chemistry Observations and Modelling, National Center for Atmospheric Research, Boulder, CO, USA
  • 4Department of Physics and Astronomy, University of Louisville, Louisville, KY, 40292, USA

Tides are crucially important to the dynamics of the MLT. Therefore, models which aim to span the whole atmosphere must be capable of reproducing these tides, making observations of tides vital to constrain model development. Here, we present a novel climatology of 12- and 24-hour tides, measured at heights of 80–100 km by a meteor radar over the Rothera Station, Antarctica (68°S, 68°W). We use these observations to test two GCMs: WACCM and eCMAM (the latter 24-hr only). Our observations reveal large-amplitude tides with strong seasonal variability. The 12-hour tide maximises around the equinoxes and the smaller-amplitude 24-hour tide maximises in summer.  WACCM reproduces 12-hour tidal amplitudes at 80 km well, but not their increase with height or equinoctial maxima, and reproduces the observed small variation in 24-hr tidal amplitude with height well but with anomalously-large amplitudes. eCMAM reproduces observed 24-hr tidal amplitudes and their small variation with height. Our observations also reveal sizeable day-to-day variability in tidal amplitude at planetary wave periods, which we suggest originates from non-linear tidal/planetary-wave coupling. Furthermore, we see notable differences between observed and model background winds which are not reproduced in the models; we propose these differences may arise from the lack of in-situ gravity-wave sources in the models.

How to cite: Dempsey, S. M., Hindley, N., Moffat-Griffin, T., Wright, C., Smith, A., Du, J., and Mitchell, N.: Winds and tides of the Antarctic mesosphere and lower thermosphere: One year of meteor-radar observations over Rothera (68°S, 68°W) and comparisons with WACCM and eCMAM, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15631, https://doi.org/10.5194/egusphere-egu21-15631, 2021.