Characteristics of Small-scale Gravity Wave Propagation in the Mesopause Region over Alaska

We investigated characteristics of the atmospheric gravity waves (AGWs) propagation using sodium airglow images obtained by an all-sky imager installed at Poker Flat Research Range (65.1N, 147.4W, MLAT 65.6) in Alaska. In this study, we developed data analysis programs which automatically derive the unambiguous 2-D power spectrum from the sodium airglow images, using a method by Coble et al. (1998). The power spectrums of the AGWs which have horizontal wavelengths between 2 - 400 km and periods up to 8 hours were obtained by these programs.

Statistical study of the AGW data and mesospheric wind data by an MF radar during two winter seasons from October 2000 to April 2002 indicates the following characteristics.

- During these periods, the AGW dominantly propagated westward in the zonal direction.

- The meridional propagation direction frequently changed. This change seems to be explained by filtering effect by the mesospheric wind.

- Total power of the AGW increased in December and January.

In this paper, we discuss the relationship between these characteristics of the AGW propagation and unique phenomena in high-latitude region such as auroral precipitation.

Acknowledgements

This work is conducted as a part of "Alaska Project", the cooperative research project between NICT and Geophysical Institute of University of Alaska.

Reference

Coble, M. R., G. C. Papen, and C. S. Gardner, Computing two-dimensional unambiguous horizontal wavenumber spectra from OH airglow images, IEEE Trans. Geosci. and Remote Sens., 36, 368--382, 1998.