Pusan National University study finds pollution shifts rainfall from land to sea in Southeast Asia

Tiny airborne particles known as aerosols, from biomass burning, urban pollution, and industrial emissions, can dramatically alter rainfall, cloud formation, and atmospheric stability. A new study led by Professor Kyong-Hwan Seo of Pusan National University, Korea, shows that aerosols profoundly reshape precipitation over the Maritime Continent, a region including Indonesia, Malaysia, Singapore, Vietnam, Thailand, the Philippines, and surrounding seas, where millions rely on predictable rainfall for water, food, and flood protection.

Published online in npj Climate and Atmospheric Science on September 25, 2025, the study combined a 2-km-resolution atmospheric model with NASA TRMM satellite data and MERRA-2 reanalysis to simulate how varying aerosol levels influence convection and precipitation. The team analyzed a 2011 Madden-Julian Oscillation event and tested other phases and years, finding that high aerosols consistently increased rainfall over the ocean while suppressing it over land.

“As aerosol concentrations rise, the precipitation pattern shifts from a land-enhanced to an ocean-dominant one,” said Seo.

In high-aerosol simulations, oceanic rainfall intensified by up to 50%, while land precipitation declined, producing a markedly higher sea-to-land rainfall ratio, a novel discovery confirmed by both model simulations and satellite observations.

The mechanism behind this shift is primarily radiative. Aerosols cool the land surface more strongly than the ocean, stabilizing the lower atmosphere over islands while leaving the sea relatively unstable. This difference enhances low-level convergence and convection at sea, drawing moisture away from land.

Seo explained, “Aerosols act like a brake on daytime heating over land, but the ocean hardly feels that brake.”

High aerosol levels also delay the peak of the diurnal precipitation cycle over land from late afternoon to around midnight, a counterintuitive pattern linked to reduced daytime heating and nighttime buildup of moist static energy.

“We’re seeing a delay from the usual late-afternoon storms to a midnight peak,” noted Seo.

Some observed high-aerosol events exhibit similar behavior, now revealed in detail through combined modeling and satellite data.

These findings carry important practical applications. In densely populated and flood-prone regions such as Jakarta or Manila, understanding aerosol-driven shifts toward more oceanic rainfall can improve disaster management, irrigation planning, and urban flood preparedness. Short-term forecasts may become more accurate during haze or pollution episodes, helping authorities allocate resources and mitigate risks to infrastructure and transportation. Incorporating these aerosol effects into climate and weather models may also improve predictions of the Madden–Julian Oscillation (MJO), monsoons, and extreme tropical rainfall events, which influence seasonal weather patterns far beyond Southeast Asia.

Over the longer term, this research could transform tropical climate forecasting. The study suggests smoother MJO propagation across the Maritime Continent by revealing how aerosols weaken land-based convection—potentially enabling more reliable seasonal rainfall predictions. These insights could support water resource management, food security, and energy planning for millions of people. On a global scale, integrating aerosol impacts into climate models could refine projections of precipitation changes amid rising emissions, helping communities reduce vulnerability to floods and droughts and adapt to climate-driven water challenges in tropical regions.

***

Reference

DOI: 10.1038/s41612-025-01215-5

About Pusan National University

Pusan National University, located in Busan, South Korea, was founded in 1946 and is now the No. 1 national university of South Korea in research and educational competency. The multi-campus university also has other smaller campuses in Yangsan, Miryang, and Ami. The university prides itself on the principles of truth, freedom, and service and has approximately 30,000 students, 1,200 professors, and 750 faculty members. The university comprises 14 colleges (schools) and one independent division, with 103 departments in all.

Website: https://www.pusan.ac.kr/eng/Main.do

About the author

Dr. Kyong-Hwan Seo is a Professor of Atmospheric Sciences and the Director of the Institute for Future Earth at Pusan National University. His research spans a broad range of topics in climate and atmospheric dynamics, tropical meteorology, climate change and modeling, aerosol–cloud–circulation interactions, and polar processes. His major areas of focus include the Hadley circulation, Madden–Julian Oscillation, Rossby wave dynamics, teleconnections, monsoon dynamics, extreme weather and climate events, and the impacts of aerosols on weather and climate. Before coming to Pusan National University, he worked as a Climate Scientist at the Climate Prediction Center/NCEP/NOAA in the USA. Kyong-Hwan Seo received a PhD in Atmospheric Sciences from Texas A&M University in 2001 and was awarded a Presidential Commendation in 2023 in recognition of contributions to monsoon dynamics.