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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 33, issue 10
Ann. Geophys., 33, 1321–1330, 2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 33, 1321–1330, 2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 30 Oct 2015

Regular paper | 30 Oct 2015

Observational evidence of quasi-27-day oscillation propagating from the lower atmosphere to the mesosphere over 20° N

K. M. Huang1,2, A. Z. Liu3, S. D. Zhang1,2, F. Yi1,2, C. M. Huang1,2, Q. Gan1,2, Y. Gong1,2, Y. H. Zhang4, and R. Wang5 K. M. Huang et al.
  • 1School of Electronic Information, Wuhan University, Wuhan, China
  • 2State Observatory for Atmospheric Remote Sensing, Wuhan, China
  • 3Department of Physical Science, Embry-Riddle Aeronautical University, Daytona Beach, Florida, USA
  • 4College of Hydrometeorology, Nanjing University of Information Science and Technology, Nanjing, China
  • 5SOA Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China

Abstract. By using meteor radar, radiosonde and satellite observations over 20° N and NCEP/NCAR reanalysis data during 81 days from 22 December 2004 to 12 March 2005, a quasi-27-day oscillation propagating from the troposphere to the mesosphere is reported. A pronounced 27-day periodicity is observed in the raw zonal wind from meteor radar. Spectral analysis shows that the oscillation also occurs in the meridional wind and temperature and propagates westward with wavenumber s = 1; thus the oscillation is of Rossby wave type. The oscillation attains a large amplitude of about 12 m s−1 in the eastward wind shear region of the troposphere. When the wind shear reverses, its amplitude rapidly decays, and the background wind gradually evolves to be westward. However, the oscillation can penetrate through the weak westward wind field due to its relatively large phase speed. After this, the oscillation restrengthens with its upward propagation and reaches about 20 m s−1 in the mesosphere. Reanalysis data show that the oscillation can propagate to the mid and high latitudes from the low latitudes and has large amplitudes over there. There is another interesting phenomenon that a quasi-46-day oscillation appears simultaneously in the troposphere, but it cannot penetrate through the westward wind field because of its smaller phase speed. In the observational interval, a quasi-27-day periodicity in outgoing long-wave radiation (OLR) and specific humidity is found in a latitudinal zone of 5–20° N. Thus the quasi-27-day oscillation may be an atmospheric response to forcing due to the convective activity with a period of about 27 days in the tropical region.

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