A Preliminary Report on Radiosonde Observations of the Equatorial Atmosphere Dynamics over Indonesia

Observations of the equatorial atmosphere dynamics by means of radiosondes were conducted, as a collaborative project between Japan and Indonesia, at the Watukosek observatory in East Jawa, Indonesia, for 25 days from 27 February to 22 March, 1990. Profiles of the wind velocity, temperature, pressure and humidity were obtained at 0-35km altitude with time and height resolutions of 5-7 hours and 150m, respectively. This paper gives an outline of the experiment and the background conditions of the atmosphere during the campaign period. The structure of the zonal mean winds at 10-25km was basically explained by QBO, showing westward winds of about 15m/s, while the meridional winds were fairly weak in the entire height range. The mean temperature profile indicated the tropopause to be at 17-18km altitude, with a minimum temperature of about 190K. Both wind velocity and temperature fluctuations were large indicating the manifestation of various wave activities. The relative humidity was fairly high in the lower troposphere, showing periodic fluctuations with time scales of 3-5 days in addition to the diurnal cycle.