Since 2007, the capital city of Indonesia, Jakarta, has experienced severe flooding resulting in significant economic losses and death. While sub-optimal urban-planning management plays some role in these events, an increase in extreme rainfall intensity is the prime cause. On occasion up to 135mm has fallen in just two days.

There is little understanding about what causes these heavy rains and this has made if difficult for the local government to mitigate or reduce risks associated with floods.

Previous research found that El Nino Southern-Oscillation (ENSO) induced some rainfall extremes. However, there has been no comprehensive study examining whether other large-scale modes of climate variability – such as the Indian Ocean Dipole (IOD) or Madden Julian Oscillation (MJO) – also generate extreme rainfall events.

To investigate this, CLEX researchers first employed quality control procedures for daily rainfall stations in this region.

Then, they found that the IOD and ENSO both play a role in the organisation of extreme rain events during the dry season (Jun-Jan). Interestingly the IOD had a stronger effect than ENSO.

By contrast, during the wet season, a large number of extreme rainfall events occurred during the active phase of MJO, especially in high-altitude sites.

This study implies that the topography, or local forcing, seems to play a key role in the development of extreme rainfall events in the region. High variations in extreme rainfall event at each site also indicate here are highly localised differences in response to large-scale conditions.

  • Paper: Lestari, S., King, A., Vincent, C., Karoly, D., Protat, A. Seasonal dependence of rainfall extremes in and around Jakarta, Indonesia. Weather and Climate Extremes. (2019).