Multiscale Interactions between the MJO, Equatorial Waves, and the Diurnal Cycle over the Maritime Continent: Part I

The major objective of this study is to investigate the interaction between the diurnal cycle and wave disturbances such as the Madden-Julian Oscillation (MJO) and other equatorial wave modes over the Maritime Continent (the MC). The MC is region, covers 20⁰S-20⁰N and 90⁰E-170⁰E, composed of a complex topography with small and large islands and exhibits significant diurnal cycle. The MJO, a dominant source of intraseasonal variability, originates over the western Indian Ocean and propagates eastward across the MC. Past studies show that the MJO weakens over the MC due to topographic effects and interactions with the diurnal cycle. We use satellite observed datasets to understand the diurnal cycle of precipitation and cloud convective systems and its association with wave disturbances, including the MJO. These observed data are from Tropical Rainfall Measurement Mission (TRMM3B42), TRMM Precipitation Features (PFs) derived from TRMM satellite sensors and weather state data from the International Satellite Cloud Climatology Project (ISCCP). Analysis using TRMM3B42 and TRMM PFs shows that diurnal cycle of precipitation peaks during late afternoon through early morning (1800LT to 0000LT) and noon through evening (1200LT to 1800LT) respectively. Weather State peaks over land region late in the afternoon through early morning mainly over Sumatra and Borneo islands. The diurnal cycle based on these datasets is stronger over land mostly during afternoon through early morning and it is strong over ocean in morning through noon local time. In this study, we will also examine the interaction between MJO, Kelvin waves, and Easterly waves with the diurnal cycle of precipitation over the MC.