AsianScientist (Dec. 24, 2025) – Rising pollution levels are pushing storms away from land and intensifying rainfall over the ocean in Southeast Asia.
Biomass burning, urban pollution, and industrial emissions produce tiny particles called aerosols that can dramatically alter rainfall, cloud formation, and atmospheric stability. Now, a new study conducted by researchers of Pusan National University, Korea, has revealed that aerosols profoundly impact rainfall patterns over the Maritime Continent, where millions rely on predictable rainfall for water, food, and flood protection.
The Maritime Continent – a region including Indonesia, Malaysia, Singapore, Vietnam, Thailand, the Philippines, and surrounding seas – and Southeast Asia, are recognized as major sources of both biomass-burning aerosol and industrial pollution, mostly due to rapid industrialization and urbanization, according to the study.
“As aerosol concentrations rise, the precipitation pattern shifts from a land-enhanced to an ocean-dominant one,” said lead author Professor Kyong-Hwan Seo, from the Department of Atmospheric Sciences, Research Center for Climate Sciences, Pusan National University.
The study combined high-resolution atmospheric modeling with NASA satellite observations to uncover how rising aerosol concentrations are shifting the region’s climate balance in unexpected ways.
How the study was conducted
To understand the impact of aerosols on weather, the researchers used a 2-km-resolution atmospheric model with NASA TRMM satellite data and MERRA-2 reanalysis, to simulate varying aerosol levels during a 2011 Madden-Julian Oscillation (MJO) event. They tested multiple phases and years, and the result was consistent: higher aerosol concentrations drive rainfall away from land and toward surrounding seas.
They found that when pollution spikes, rainfall grows up to 50 percent more intense over the ocean, while land rainfall drops sharply.
Why rain shifts from land to sea
The shift, the team found, is driven by how aerosols cool the environment. Pollution cools land surfaces much more than the ocean, calming the atmosphere over islands while leaving the air over the sea unstable. This contrast strengthens rising air and storm activity over the ocean, pulling moisture away from land.
“Aerosols act like a brake on daytime heating over land, but the ocean hardly feels that brake,” Seo explained.
Pollution also disrupts the region’s natural daily rainfall rhythm. Instead of the usual late-afternoon storms over land, high aerosol levels delay peak rainfall until around midnight. This occurs because polluted air limits daytime heating, allowing heat and moisture to accumulate and trigger storms later in the night.
Similar delayed and offshore rainfall patterns have been observed during real high-pollution events.
What this means for forecasting and flood preparedness
The researchers say that the findings, published in npj Climate and Atmospheric Science, hold major implications for weather prediction and climate resilience in a region already vulnerable to extreme rainfall and flooding.
“Cities like Jakarta and Manila could benefit from improved short-term rainfall forecasts during haze episodes or pollution episodes, helping authorities prepare for urban flooding, allocate resources and mitigate risks to infrastructure and transportation,” the researchers state.
Incorporating aerosol effects into climate models may also improve predictions of the MJO, monsoon systems, and extreme tropical rainfall events. Over the long term, the research suggests that weakened land-based convection could allow the MJO to move more smoothly across the Maritime Continent, improving seasonal rainfall forecasts.
These insights, the researchers say, could strengthen water management, food security, and energy planning for millions across Southeast Asia.
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Source: Pusan National University; Image: EyeEm/Freepik
The study can be found at: Aerosol effects on Maritime Continent precipitation: Oceanic intensification and land diurnal cycle delay
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