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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 32, issue 9
Ann. Geophys., 32, 1129–1143, 2014
https://doi.org/10.5194/angeo-32-1129-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 32, 1129–1143, 2014
https://doi.org/10.5194/angeo-32-1129-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 12 Sep 2014

Regular paper | 12 Sep 2014

Spatial and seasonal variability of medium- and high-frequency gravity waves in the lower atmosphere revealed by US radiosonde data

S. D. Zhang4,3,2,1, C. M. Huang4,3,2,1, K. M. Huang4,3,2,1, F. Yi4,3,2,1, Y. H. Zhang5, Y. Gong4,3,2,1, and Q. Gan4,3,2,1 S. D. Zhang et al.
  • 1School of Electronic Information, Wuhan University, Wuhan, Hubei, People's Republic of China
  • 2Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan, Hubei, People's Republic of China
  • 3State Observatory for Atmospheric Remote Sensing, Wuhan, People's Republic of China
  • 4State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan, People's Republic of China
  • 5College of Hydrometeorology, Nanjing University of Information Science and Technology, Nanjing, People's Republic of China

Abstract. 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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