The intraseasonal behaviors of outgoing long wave radiation (OLR) obtained from polar orbiting satellites are investigated for the period from January through November 1979.
The power spectrum of the OLR data for the whole period has revealed the existence of 30-60 day and 15-25 day periodicities. The intense power for the 30-60 day period range appears over southern Indonesia to northern Australia during the Southern Hemisphere summer, and over South Asia during the Northern Hemisphere summer.
The relationship between the intraseasonal variations and tropical cyclone activities was analyzed. In most cases during both hemisphere summers, the generation and growth of tropical cyclones occur during the active phase of the intraseasonal variations.
The relationship between the intraseasonal variations and short-period (3-10 days) fluctuations was also investigated. The 3-10 day fluctuations show clear amplitude modulation with 30-60 day period which is the same periodicity as the intraseasonal variations. The amplitude of short-period fluctuations becomes large (small) during the active (break) phase of the intraseasonal variations. Eastward moving wavenumber 1 component is prominent for the amplitude modulation of the 3-10 day fluctuations with 30-60 day period.