Evidence for Low-Frequency Waves of Tropical Rainfall Inferred from Microwave Brightness Temperature

Abstract

Evidence for the 30?60-day oscillation was found in the rainfall data that were retrieved from Special Sensor Microwave/Imager brightness temperatures from January to December 1989. Spectral analysis of daily rainfall showed that the strongest rainfall oscillations were located from 5°S to 5°N and extend from about 60°E to 180°. The oscillation propagated eastward at a speed of approximately 4 m s?1 along the equatorial Indian?western Pacific Ocean area. Northward propagation at a speed of about 1.5 m s?1 was also detected from 15°S to 30°N over the Indian Ocean between early May and late July.