Not La Niña or IOD, IPB University Meteorologist Says Sunspot Activity is the Cause of Wet Drought
Indonesia is currently experiencing a wet dry season. An unusual weather condition characterized by high rainfall despite the onset of the dry season.
According to IPB University Meteorologist Sonni Setiawan, SSi, MSi, this phenomenon is not only related to monsoon patterns and global climate anomalies but is also influenced by solar activity, particularly sunspots.
“Scientifically, the term season is defined based on the apparent position of the sun relative to an observer on the Earth’s surface. When the sun is south of the equator or in the Southern Hemisphere (SH), the southern part of the Earth receives more intense solar radiation,” he explained.
He further elaborated that solar radiation heating in the Southern Hemisphere causes the air in the SH to have lower pressure compared to the air pressure in the NH, resulting in winds moving from the NH to the SH. The same applies when the sun is north of the equator or in the Northern Hemisphere (NH). “This is the seasonal cycle,” he said.
However, this lecturer from the Department of Geophysics and Meteorology, Faculty of Mathematics and Natural Sciences (FMIPA) at IPB University revealed that the current conditions deviate from the normal pattern.
“Normally, during the dry season, rainfall decreases. But now, it’s raining continuously. This is what’s called a wet dry season,” he added.
Climate Anomalies and Solar Activity
Sonni explained that the wet dry season phenomenon can be caused by various factors. Some of these include global climate phenomena such as El Niño and La Niña, as well as the Indian Ocean Dipole (IOD).
However, he revealed that La Niña—characterized by cooling sea temperatures in the central and eastern Pacific Ocean—is currently detected in weak to moderate conditions and contributes to increased rainfall during the dry season.
Meanwhile, the IOD—which indicates differences in sea temperatures in the Indian Ocean—is in a neutral state. Therefore, Sonny said, its impact on this year’s wet dry season is relatively small.
“Currently, there are no strong indications of El Niño or La Niña, nor of the IOD. What is interesting is the 11-year cycle of sunspot activity, which has been at its peak since 2024 and will remain active in 2025,” he said.
Sunspots are dark spots on the sun’s surface indicating high radiation activity. When sunspots increase, the sun emits more high-energy particles such as cosmic rays. These particles can accelerate condensation processes in the atmosphere and enhance cloud formation, thereby increasing the likelihood of heavy rain.
“Sunspots also increase the electrical potential gradient within clouds, making thunderstorms more frequent. This is one of the factors contributing to increased rainfall, even during the dry season,” said Sonni.
Impact on Flooding and Agriculture
Sonny noted that the wet dry season has significant impacts on various sectors. In the agricultural sector, this phenomenon can cause losses. Certain crops that are sensitive to high humidity may experience reduced quality and yield.
“Additionally, cropping patterns adapted to the dry season are disrupted due to unpredictable rainfall,” he added.
Furthermore, he noted, the wet dry season phenomenon also poses a risk of tidal flooding in northern coastal areas of Java, such as Pekalongan, Semarang, and North Jakarta.
“Tidal flooding is actually caused by the rise in sea levels due to the moon’s gravitational pull. However, when heavy rain falls continuously and coincides with maximum tidal levels, the volume of water entering the land increases drastically,” explained Sonni.
This situation is exacerbated by land subsidence in some coastal areas caused by excessive groundwater extraction. “Sea walls are insufficient if the land is already lower than sea level. This exacerbates the risk of tidal flooding,” he added.
In addition to sunspots, other atmospheric phenomena such as the Madden Julian Oscillation (MJO), Kelvin waves, and Rossby waves also contribute to rainfall anomalies.
“These phenomena modulate the intensity of extreme rainfall in the short term and can amplify rainfall effects during the dry season,” Sonni concluded. (Fj) (IAAS/LAN)
