Abstract
An inertial gravity wave related to a synoptic-scale pressure trough was revealed by observations made with the MU radar. Twelve beams were used to scan zonally to detect the spatial variation of the wind. According to hodograph analysis and theoretical considerations, the gravity wave propagated downward from the tropopause height of 11km, had a horizontal wavelength of 300km and a horizontal phase velocity of 20m/s. The estimated parameters are consistent with all information obtained by the measurements.
The height-time section of the echo power shows that a severe turbulent layer was located near the tropopause height while the wave was appearing. A large vertical shear in the horizontal wind was coincidently observed at the same altitude. This suggests that the inertial gravity wave originated from the atmosphere having low stability near the tropopause. During the measurements with the MU radar, a synoptic-scale pressure trough passed near the radar site. The gravity wave was observed just before the northward wind migrated. These results indicate that the synoptic-scale pressure trough is one of the possible sources of gravity waves.
