Transient eastward-propagating long-period waves observed over the South Pole
Observations of the horizontal wind field over the South Pole were made during 1995 using a meteor radar. These data have revealed the presence of a rich spectrum of waves over the South Pole with a distinct annual occurrence. Included in this spectrum are long-period waves, whose periods are gr...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
1998-11-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/16/1486/1998/angeo-16-1486-1998.pdf |
| _version_ | 1818609074406686720 |
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| author | S. E. Palo Y. I. Portnyagin J. M. Forbes N. A. Makarov E. G. Merzlyakov |
| author_facet | S. E. Palo Y. I. Portnyagin J. M. Forbes N. A. Makarov E. G. Merzlyakov |
| author_sort | S. E. Palo |
| collection | DOAJ |
| description | Observations of the horizontal wind field
over the South Pole were made during 1995 using a meteor radar. These data have
revealed the presence of a rich spectrum of waves over the South Pole with a
distinct annual occurrence. Included in this spectrum are long-period waves,
whose periods are greater than one solar day, which are propagating eastward.
These waves exhibit a distinct seasonal occurrence where the envelope of wave
periods decreases from a period of 10 days near the fall equinox to a minimum of
2 days near the winter solstice and then progresses towards a period near 10
days at the spring equinox. Computation of the meridional gradient of
quasi-geostrophic potential vorticity has revealed a region in the high-latitude
upper mesosphere which could support an instability and serve as a source for
these waves. Estimation of the wave periods which would be generated from an
instability in this region closely resembles the observed seasonal variation in
wave periods over the South Pole. These results are consistent with the
hypothesis that the observed eastward propagating long-period waves over the
South Pole are generated by an instability in the polar upper mesosphere.
However, given our limited data set we cannot rule out a stratospheric source.
Embedded in this spectrum of eastward propagating waves during the austral
winter are a number of distinct wave events. Eight such wave events have been
identified and localized using a constant-<i>Q</i> filter bank. The periods of
these wave events ranges from 1.7 to 9.8 days and all exist for at least 3 wave
periods. Least squares analysis has revealed that a number of these events are
inconsistent with a wave propagating zonally around the geographic pole and
could be related to waves propagating around a dynamical pole which is offset
from the geographic pole. Additionally, one event which was observed appears to
be a standing oscillation.<br><br><b>Key words.</b> Meteorology and atmospheric dynamics (Middle
atmospheric dynamics; waves and tides). |
| first_indexed | 2024-12-16T14:52:45Z |
| format | Article |
| id | doaj.art-5a0237e78c90489194d4f8e8c5a09b49 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-16T14:52:45Z |
| publishDate | 1998-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-5a0237e78c90489194d4f8e8c5a09b492022-12-21T22:27:33ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05761998-11-01161486150010.1007/s00585-998-1486-7Transient eastward-propagating long-period waves observed over the South PoleS. E. Palo0Y. I. Portnyagin1J. M. Forbes2N. A. Makarov3E. G. Merzlyakov4University of Colorado, Boulder, CO, USAInstitute for Experimental Meteorology, Obninsk, RussiaUniversity of Colorado, Boulder, CO, USAInstitute for Experimental Meteorology, Obninsk, RussiaInstitute for Experimental Meteorology, Obninsk, RussiaObservations of the horizontal wind field over the South Pole were made during 1995 using a meteor radar. These data have revealed the presence of a rich spectrum of waves over the South Pole with a distinct annual occurrence. Included in this spectrum are long-period waves, whose periods are greater than one solar day, which are propagating eastward. These waves exhibit a distinct seasonal occurrence where the envelope of wave periods decreases from a period of 10 days near the fall equinox to a minimum of 2 days near the winter solstice and then progresses towards a period near 10 days at the spring equinox. Computation of the meridional gradient of quasi-geostrophic potential vorticity has revealed a region in the high-latitude upper mesosphere which could support an instability and serve as a source for these waves. Estimation of the wave periods which would be generated from an instability in this region closely resembles the observed seasonal variation in wave periods over the South Pole. These results are consistent with the hypothesis that the observed eastward propagating long-period waves over the South Pole are generated by an instability in the polar upper mesosphere. However, given our limited data set we cannot rule out a stratospheric source. Embedded in this spectrum of eastward propagating waves during the austral winter are a number of distinct wave events. Eight such wave events have been identified and localized using a constant-<i>Q</i> filter bank. The periods of these wave events ranges from 1.7 to 9.8 days and all exist for at least 3 wave periods. Least squares analysis has revealed that a number of these events are inconsistent with a wave propagating zonally around the geographic pole and could be related to waves propagating around a dynamical pole which is offset from the geographic pole. Additionally, one event which was observed appears to be a standing oscillation.<br><br><b>Key words.</b> Meteorology and atmospheric dynamics (Middle atmospheric dynamics; waves and tides).https://www.ann-geophys.net/16/1486/1998/angeo-16-1486-1998.pdf |
| spellingShingle | S. E. Palo Y. I. Portnyagin J. M. Forbes N. A. Makarov E. G. Merzlyakov Transient eastward-propagating long-period waves observed over the South Pole Annales Geophysicae |
| title | Transient eastward-propagating long-period waves observed over the South Pole |
| title_full | Transient eastward-propagating long-period waves observed over the South Pole |
| title_fullStr | Transient eastward-propagating long-period waves observed over the South Pole |
| title_full_unstemmed | Transient eastward-propagating long-period waves observed over the South Pole |
| title_short | Transient eastward-propagating long-period waves observed over the South Pole |
| title_sort | transient eastward propagating long period waves observed over the south pole |
| url | https://www.ann-geophys.net/16/1486/1998/angeo-16-1486-1998.pdf |
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