Intraseasonal Change in Diurnal Cycle of Precipitation over Sumatra from IMERG Observation

Abstract

This study investigates the intraseasonal change in the diurnal cycle of rainfall over Sumatra in terms of Madden Julian oscillation (MJO) phases. Change in the peak time of mean accumulation (PA), frequency (PF), and intensity (PI) of precipitation from Integrated Multi-Satellite Retrievals of GPM (IMERG) final run product version 06 data during 2016-2019 was investigated. Data were classified into active (2,3,4, and 5) and inactive (1,6,7 and 8) MJO. Rainfall in the Sumatra region is generally dominated by short rainfall duration, as found by a previous study. During the active MJO, the increase the number of rain events over the mainland Sumatra is dominated by rain lasting less than 6 h. In the Indian Ocean region, the increase in rain events is dominated by short and long-duration rain. The means of PA and PF during the active MJO showed a significant increase (0.4 mm/h and 10%), especially in the western part of Sumatra. On the other hand, the average PI during the active MJO tends to decrease (~ 1.5 mm/h), especially in the southern mainland of Sumatra. Finally, we found no significant change in the peak time of PA, PF, and PI during the active MJO and inactive MJO.