Abstract
The dominance of 1.5-2.5-day variance in the cloud field in the December-February season and its characteristic features are described in detail utilizing three-hourly infrared blackbody temperature data obtained by the Japanese Geostationary Meteorological Satellite.
It is shown that 1.5-2.5 day-period cloud system possesses the properties of n=1 westward-propagating inertio-gravity waves. The dominant zonal wavelength is 30°-40° and the propagation speed is 20-30ms-1 relative to the 850hPa mean wind. The equivalent depth of ∼20m was indicated from the composite analysis and from the spectral analysis. Significant correlation of 1.5-2.5-day-period mode with the total cloud variance suggests that this mode always accompanies equatorial cloud activity. Eastward-propagating n=1 inertio-gravity waves were, on the other hand, not observed.
