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| Titel |
Seasonal and nightly variations of gravity-wave energy density in the middle atmosphere measured by the Purple Crow Lidar |
| VerfasserIn |
R. J. Sica, P. S. Argall |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 25, no. 10 ; Nr. 25, no. 10 (2007-11-06), S.2139-2145 |
| Datensatznummer |
250015928
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| Publikation (Nr.) |
 copernicus.org/angeo-25-2139-2007.pdf |
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| Zusammenfassung |
| The Purple Crow Lidar (PCL) is a large power-aperture product monostatic
Rayleigh-Raman-Sodium-resonance-fluorescence lidar, which has been in
operation at the Delaware Observatory (42.9° N, 81.4° W, 237 m
elevation) near the campus of The University of Western Ontario since 1992.
Kinetic-energy density has been calculated from the Rayleigh-scatter system
measurements of density fluctuations at temporal-spatial scales relevant for
gravity waves, e.g. soundings at 288 m height resolution and 9 min temporal
resolution in the upper stratosphere and mesosphere. The seasonal averages
from 10 years of measurements show in all seasons some loss of gravity-wave
energy in the upper stratosphere. During the equinox periods and summer the
measurements are consistent with gravity waves growing in height with little
saturation, in agreement with the classic picture of the variations in the
height at which gravity waves break given by Lindzen (1981). The mean values
compare favourably to previous measurements when computed as nightly
averages, but the high temporal-spatial resolution measurements show
considerable day-to-day variability. The variability over a night is often
extremely large, with typical RMS fluctuations of 50 to 100% at all
heights and seasons common. These measurements imply that using a daily or
nightly-averaged gravity-wave energy density in numerical models may be
highly unrealistic. |
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