Seasonal dependence of rainfall extremes in and around Jakarta, Indonesia

This study investigates the interannual, seasonal, and intraseasonal variation in rainfall extremes (REs) in Jakarta and surroundings. We used datasets of daily rainfall at three sites at coastal, inland and mountainous environments during 1974-2016 (42 years), Sea Surface Temperature, 850-hPa zonal and meridional winds, and Outgoing Longwave Radiation during 1979-2016 (37 years). The results show that intensity and frequency of REs, and their relative contribution to the total rainfall, have strong relationships with the Indian Ocean Dipole and El Nino Southern Oscillation in the dry season (Jun-Nov) but weak relationships in the wet season (Dec-May) at all sites. During active Madden-Julian Oscillation (MJO) period, the daily average rainfall and the number of RE days relative to all days show strong variation between MJO phases at all sites and the MJO signature differs between the three stations. At the coastal and inland sites, there is a less marked variation of the number of RE events relative to all days with MJO phases. Compared to lower altitudes, the high-altitude station has a greater number of RE events relative to all days in the wet season and a lower intensity of REs relative to total rainfall amount in the dry season. The results of the study suggest that the REs vary in each station due to highly localised differences in responses to large-scale conditions.