Spectra of the OH Airglow Perturbation on 5 Januray 2009 at Langfang

It is necessary to observe and analyze the characters of gravity waves to study their effect to upper and middle atmosphere. The first imaging observation experiment of the atmospheric gravity waves in the mesopause region in China with the all-sky OH band airglow CCD imager is made on 5 January 2009, at Hancun (39.4°N, 116.6°E), Langfang, Hebei. Based on the nearly 4-hour data, we obtained the specta of OH airglow perturbation during this time period, with a horizontal range of about 185 km centered around the observatory (at Hancun, Langfang). The unambiguous power spectrum and angular spectrum method is approved by simulation. The parameters of three quasi-monochromatic gravity waves analyzed before agree with the unambiguous power spectrum. The unambiguous power spectrum and angular spectrum reveal the distribution of wavelengths and propagation directions of the gravity waves during the 4 hours: the lower limit of wavelength is short; the gravity waves propagate more west than in the east. Compared with the results in other two papers, the directions are different in different sites even in the same season and similar altitudes, which may be related with the different sources of the gravity waves.