TEMPO.CO, Jakarta - Rain has continued to shower over the greater Jakarta area, Banten, and West Java for the past week despite initial weather forecasts suggesting the dry season will peak in June. According to the BRIN climate and atmosphere researcher Didi Setiadi, this situation is largely due to the Rossby wave’s wet phase lasting between 7 to 10 days.

“However, it now seems to be declining,” Setiadi wrote in a text on June 20.

Based on an analysis on June 16 from ventusky.com, disturbances of low-pressure centers and cyclonic circulation in the Indian Ocean, the system will form wind and water vapor convergence, cloud growth, and rain, especially in the area around West Java, the Sunda Strait, and Lampung.

Didi sees that apart from cyclonic circulation disturbances which started to weaken on June 20, the Rossby Atmospheric Wave has been observed active in Indonesian territory at this time with a water vapor content over Indonesian territory.

The Rossby wave is one of the atmospheric waves in the equatorial region that moves westward with a period of less than 72 days and can last up to 7-10 days. There is an increase in the water vapor content which increases the potential for cloud growth and rain emerges during an active Rossby wave period.

"At least rain reduces pollution as it would have increased during the dry season," said Didi.

Temperature

In contrast to the rain-stricken Jabodetabek and surrounding areas, the western tip of Indonesia, such as Banda Aceh to be precise, is repeatedly predicted to experience the highest temperature in Indonesia up to 36 degrees Celsius on June 20.

According to Didi, an increase in cloud growth will generally lower surface temperatures.

"Clouds behave like umbrellas that prevent solar radiation from reaching the earth's surface," he explained. Meanwhile, areas with few clouds, such as Aceh, will experience maximum temperatures, especially during the day.

MARIA FRANSISCA LAHUR

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