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| Titel |
Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data |
| VerfasserIn |
S. D. Zhang, C. M. Huang, K. M. Huang, F. Yi, Y. H. Zhang, Y. Gong, Q. Gan |
| 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 ; 32, no. 9 ; Nr. 32, no. 9 (2014-09-12), S.1129-1143 |
| Datensatznummer |
250121107
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| Publikation (Nr.) |
 copernicus.org/angeo-32-1129-2014.pdf |
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| Zusammenfassung |
| We extended the broad spectral method proposed by Zhang
et al. (2013) for the extraction of medium- and high-frequency gravity waves
(MHGWs). This method was applied to 11 years (1998–2008) of radiosonde data from
92 stations in the Northern Hemisphere to investigate latitudinal,
continuous vertical and seasonal variability of MHGW parameters in the lower
atmosphere (2–25 km). The latitudinal and vertical distributions of the wave
energy density and horizontal momentum fluxes as well as their seasonal
variations exhibit considerable consistency with those of inertial gravity
waves. Despite the consistency, the MHGWs have much larger energy density,
horizontal momentum fluxes and wave force, indicating the more important
role of MHGWs in energy and momentum transportation and acceleration of the
background. For the observed MHGWs, the vertical wavelengths are usually
larger than 8 km; the horizontal wavelengths peak in the middle troposphere
at middle–high latitudes. These characteristics are obviously different from
inertial gravity waves. The energy density and horizontal momentum fluxes
have similar latitude-dependent seasonality: both of them are dominated by a
semiannual variation at low latitudes and an annual variation at middle
latitudes; however at high latitudes, they often exhibit more than two peaks
per year in the troposphere. Compared with the inertial GWs, the derived
intrinsic frequencies are more sensitive to the spatiotemporal variation of
the buoyancy frequency, and at all latitudinal regions they are higher in
summer. The wavelengths have a weaker seasonal variation; an evident annual
cycle can be observed only at middle latitudes. |
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