A concentric gravity wave structure in the mesospheric airglow images

A concentric gravity wave pattern was observed by an all-sky airglow imager located at Shigaraki, Japan (34.9 degrees N, 136.1 degrees E) on 3 October 2002. The wave pattern was identified over 2.5 hours (1330-1600 UT or 2230-0100 LT) both in the OI (557.7 nm) and OH (720-910 nm) band images. It had a wavelength of about 35 km and propagated concentrically northeastward with a horizontal phase velocity of about 80 m/s. The wave had a short period of about 7 min and a momentum flux of 2.2 m(2)/s(2). We identified the source of the waves as a cumulonimbus in the satellite cloud images and in radar precipitation images near the center of the concentric pattern. We conclude that this rare wave pattern was caused by a weak wind system that extended from the stratosphere to the mesopause region in an autumn transition.