Rocketsonde observations of the middle atmosphere dynamics at uchinoura(31°N,131°E) During the DYANA campaign. Part II: Characteristics of gravity waves

We describei n this paper the height variationso f the gravity wave characteristicsi n the middle atmosphere, using the profiles of wind velocity and temperature collected at 20-90 km altitude by means of a series of rocketsonde experiments and the MU (middle and upper atmosphere) radar during the DYANA campaign. The dominant vertical scales of the wind velocity fluctuations generally increased with altitude from 2 -3 km in the lower stratosphere to 10-15 km in the mesosphere. The vertical wave number spectra of the wind velocity fluctuations, constructed in five altitude regions, showed height variations in the spectral shape, which was fairly consistent with the model spectrum based upon the saturation of gravity waves. The wind velocity variance due to gravity waves generally increased in the stratosphere, diminished just above the stratopause, greatly increased again in the lower mesosphere, and finally became nearly constant in the upper mesosphere above about 65 km. The gravity waves with relatively small vertical scales were significantly weakened just above the stratopause, suggesting the important effect of the vertical structure of the static stability on the propagation characteristics of gravity waves.