The wintertime two-day wave in the polar stratosphere, mesosphere and lower thermosphere
Sandford, D. J., Schwartz, M. J. and Mitchell, N. J., 2008. The wintertime two-day wave in the polar stratosphere, mesosphere and lower thermosphere. Atmospheric Chemistry & Physics, 8 (3), pp. 749-755.
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Recent observations of the polar mesosphere have revealed that waves with periods near two days reach significant amplitudes in both summer and winter. This is in striking contrast to mid-latitude observations where two-day waves maximise in summer only. Here, we use data from a meteor radar at Esrange (68 degrees N, 21 degrees E) in the Arctic and data from the MLS instrument aboard the EOS Aura satellite to investigate the wintertime polar two-day wave in the stratosphere, mesosphere and lower thermosphere. The radar data reveal that mesospheric two-day wave activity measured by horizontal-wind variance has a semi-annual cycle with maxima in winter and summer and equinoctial minima. The MLS data reveal that the summertime wave in the mesosphere is dominated by a westward-travelling zonal wavenumber three wave with significant westward wavenumber four present. It reaches largest amplitudes at mid-latitudes in the southern hemisphere. In the winter polar mesosphere, however, the wave appears to be an eastward-travelling zonal wavenumber two, which is not seen during the summer. At the latitude of Esrange, the eastward-two wave reaches maximum amplitudes near the stratopause and appears related to similar waves previously observed in the polar stratosphere. We conclude that the wintertime polar two-day wave is the mesospheric manifestation of an eastward-propagating, zonal-wavenumber-two wave originating in the stratosphere, maximising at the stratopause and likely to be generated by instabilities in the polar night jet.
|Creators||Sandford, D. J., Schwartz, M. J. and Mitchell, N. J.|
|Departments||Faculty of Engineering & Design > Electronic & Electrical Engineering|
|Additional Information||ID number: ISI:000253908300022|
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