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Jakarta's Great Floods and History of Early Rains in Coastal Areas
21 Jun 2020

Atmospheric Science Researcher with Climatology and Climate Change Expertise at the Center for Atmospheric Science and Technology National Institute of Aviation and Space (LAPAN) Erma Yulihastin said early morning rain on the coast has been statistically proven to be related to extreme rain that has triggered major floods in the DKI Jakarta, such as the Jakarta floods of 2002, 2004, 2007, 2008, 2013 and 2014.

Erma synthesized three phenomena, namely early morning rain in the coastal region, CENS, and CT, which turned out to be related to one another.

"We certainly still remember, at the beginning of 2020 there was a big flood in Jakarta and its surroundings which was triggered by extreme rain that occurred in the early hours of the morning," Erma explained in her written statement Bandung, Saturday, June 20, 2020.

According to Erma, the early morning rain that occurred in the coastal areas raised in her dissertation was an important research problem. Because it has provided new knowledge about the characteristics of diurnal rain (rain in a span of 24 hours-ed) in coastal areas.

Erma has proven that the frequency of morning rain events on the north coast of West Java is significant at 45 percent.

"That extreme early morning rainfall event was apparently caused by anomalies that occurred on the surface of the atmosphere and the sea in the Java Sea and South China Sea, which is located north of Jakarta," said Erma.

Erma explained the anomaly in the atmosphere known as CENS was seen from the surge of strong surface wind flow from the South China Sea. Then experienced strong penetration until it reached the northern coast of western Java, including the Jakarta area.

So far, continued Erma, CENS has a major role in triggering strong convection activities that generate extreme rain that causes massive floods in Jakarta.

"However, the effect of CENS can be strengthened by the phenomenon of CT, which is the mass flow of cold water from the South China Sea near the west coast of Vietnam and spread to the Java Sea as sea surface temperatures cool," explained Erma.

Thus CT that occurs in conjunction with CENS can exacerbate extreme rainfall events at dawn. So that the effects of flooding can be even worse.

A review of the CENS-CT event, which is associated with early morning rain in Erma's dissertation, has contributed knowledge about atmospheric-sea interactions in the South China Sea in influencing variations in diurnal rainfall patterns in northern western Java.

"Proving that diurnal variation in rainfall is related to changes in amplitude, frequency, phase, duration, and location of rainfall," said Erma.

In addition to the scientific aspects, Erma's dissertation has also contributed practically by producing important recommendations for improving the accuracy of extreme weather early warning systems for DKI Jakarta.

"The CENS-CT index not only needs to be monitored continuously in real time but it is also predicted for the next 5 days."

Erma Yulihastin won a doctorate with the title Cum Laude in the Earth Science Study Program, Bandung Institute of Technology (ITB), after defending her doctoral dissertation entitled, "Variation in the Diurnal Rainfall Cycle Phase in the North Coast of West Java and its Relation to the Cross Equatorial Northerly Surge Phenomenon. (CENS) - Cold Tongue (CT) "on Friday (19/6) at the ITB Rectorate Building, Bandung, West Java.

News source: Liputan 6.

Cover image source: Modul Pusdiklat BMKG.




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