Explaining heavy rains, floods in Indonesia
By Yopi Ilhamsyah
Heavy rains in March have resulted in floods across the country. The Kompas newspaper in its March 8 edition reported that, according to the National Authority for Disaster Management (BNPB), there were 15 affected districts in East Java alone, with Madiun being the worst-hit.
BNPB spokesperson Sutopo Purwo Nugroho and National Agency for Meteorology, Climatology and Geophysics (BMKG) head of meteorology Mulyono R. Prabowo explained that the high intensity of rainfall was due to the Madden-Julian oscillation (MJO).
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It is considered as west-east circulation, originating from the Indian Ocean and vanishing in the western Pacific. The MJO is a convergent system that has an oscillation period of 30-60 days. It is identified as massive cumulonimbus clouds that occur during the transition period from March to May. Strong solar radiation quickly heats up the ocean, causing higher temperature at the surface. As stated above, this fuels on the growth of deep convective clouds, and pressure gradient causes the towering clouds accompanied by intense rainfall to move eastward across Indonesia. Above normal rainfall is recorded as it the resulting weather passes. If the environmental conditions are bad, it subsequently causes floods. The situation becomes worse when the MJO and La-Niña signals appear simultaneously.
The MJO is monitored with the MJO index, which is accessible online through the Australian Bureau of Meteorology. In March 2019, an MJO signal was detected to propagate above Indonesia and its surrounding area. High strength is indicated when the signal is outside of the centered circle. A strong signal has been observed to appear as intense rainfall occurs over Java. The whole Indonesian region is prone to the MJO, but due to southern cyclonic rotation, humid air is particularly attracted to the region of Java.
Rather than La Niña, the MJO may turn into a major climate threat, since it occurs intraseasonally. The MJO could occur more frequently amid climate change. As weather is a natural phenomenon, impact-based warning could be based on predicted monitoring. It could be both climate and floods forecasting.
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