Diurnal Cycle of Rainfall over Indonesia during ENSO Events as Observed by TRMM Satellite

Abstract

The phase and amplitude of the diurnal cycle of rainfall over Indonesia during El Niño Southern Oscillation (ENSO) events have been investigated using Tropical Rainfall Measuring Mission (TRMM) satellite observation datasets (3B42). The warm ENSO event (El Niño) and the cool event (La Niña) were selected based on the Oceanic Niño Index (ONI) for the period of 2001–2010. Harmonic analysis was used to detect the spatial and temporal variability of the diurnal cycle of rainfall for each event, and F-test was used to compare the 3B42 data during both events. Based on the ONI values, the period of June 2009–May 2010 and July 2007–June 2008 were selected for the El Niño and La Niña event respectively. The harmonic analysis results show that the diurnal cycle of rainfall is dominantly exhibited over Indonesia during both events with 73% and 74% explained variance for the El Niño and La Niña event respectively. The spatial-temporal distributions of the diurnal cycle are apparently not changed during both events. In general, large amplitude of diurnal cycle is exhibited over land with afternoon peak [1800–2100 Local Solar Time (LST)] and small amplitude is exhibited over ocean with morning peak (0900–1200 LST). Whereas over coastal area, midnight-early morning peak (0000–0300 LST) is exhibited with moderate amplitude. F-test with 95% confidence level ensures that generally there is no significant different variation of diurnal cycle of rainfall over Indonesia during both ENSO events.