A climatology of tides and gravity wave variance in the MLT above Rothera, Antarctica obtained by MF radar
A cumulative total of over 5 years of data from an MF radar situated at Rothera (67°S, 68°W) on the Antarctic Peninsula have been used to derive climatologies of periodic motions in the wind field in the mesosphere and lower thermosphere with periods less than or equal to 1 day. Strong tidal motions...
| Published in: | Journal of Atmospheric and Solar-Terrestrial Physics |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | unknown |
| Published: |
Elsevier
2007
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| Subjects: | |
| Online Access: | http://nora.nerc.ac.uk/id/eprint/3110/ https://doi.org/10.1016/j.jastp.2006.10.009 |
| Summary: | A cumulative total of over 5 years of data from an MF radar situated at Rothera (67°S, 68°W) on the Antarctic Peninsula have been used to derive climatologies of periodic motions in the wind field in the mesosphere and lower thermosphere with periods less than or equal to 1 day. Strong tidal motions are observed at 24, 12 and 8 h and monthly mean climatologies are presented between 74 and 94 km altitude for comparison with the HWM-93 horizontal wind model. The 24 h tide shows a strong seasonal dependence in both the zonal and meridional components with a summertime maximum and wintertime minimum over all altitudes. The monthly mean maximum amplitude is 12(±2) ms−1 at 94 km in January and the minimum is <1 ms−1 around 86 km in early winter. The 12 h wave shows large short-term amplitude variability with a peak in amplitude around late autumn. It reaches a minimum at high altitudes in winter and below 80 km during summer, characteristic of a mixture of migrating and non-migrating modes. The phase of the 12 h wave is relatively constant throughout winter with a minimum mean vertical wavelength of 75 km around equinox. The 8 h wave is predominantly a summertime high altitude phenomenon. It is seen most strongly in the winds above 85 km and reaches monthly mean amplitudes of 6(±2) ms−1 in the zonal winds at 94 km altitude. Finally, a seasonal climatology of gravity wave variances is generated by calculating the daily mean variance in the raw winds after subtracting the fitted tidal components. This index shows a strong seasonal and height dependence in both components with a wintertime peak of 2000 m2s−2 in the zonal component at the highest altitudes. This peak occurs when the stratospheric zonal jets are strongest and therefore the filtering of upward-propagating waves in the stratosphere should be greatest; implying that either a significant part of this wintertime wave activity is generated from a region above the peak stratospheric wind or that there is a strong annual variability in the source or propagation ... |
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