Characteristics of Kelvin waves and gravity waves observed with radiosondes over Indonesia

Profiles of wind velocity and temperature at 0–35 km were observed by means of radiosondes in west Java, Indonesia, during November 1992 and April 1993 and used to study the behavior of various atmospheric waves in the equatorial atmosphere. An oscillation, of zonal winds with a period of about 27 days was found in the troposphere, which was associated with variations in humidity and cloud top height. Kelvin waves showed phase progression beginning at cloud top height (13–16 km) and were particularly enhanced near the tropopause. The Kelvin waves strongly modulated the tropopause structure including the tropopause height, minimum temperature, and atmospheric stability. A hodograph analysis was applied to determine the propagation characteristics of inertial gravity waves. Height variation of the vertical group velocity suggests that the gravity waves were generated in the troposphere, while the horizontal phase velocity distribution suggests that they were interacting with the background mean zonal winds. These wave activities were enhanced when tall, convective clouds passed over the site, suggesting that cumulus convection seems to play a key role in generating these waves in the equatorial region.