Researchers discover role Saharan dust plays in hurricane rainfall

KALAMAZOO, Mich.—Dust in the wind. That could be the difference between a minimally impactful hurricane and one capable of producing catastrophic rain like the Southeast United States saw from Tropical Storm Debby.

A recent study led by Dr. Laiyin Zhu, associate professor in Western Michigan University's School of Environment, Geography and Sustainability, discovered Saharan dust, which travels thousands of miles across the Atlantic, plays a leading role in controlling hurricane rainfall from the Caribbean to the Gulf of Mexico and up the east coast of the U.S.. And the groundbreaking work completed by Zhu and his collaborators from California Institute of Technology, Purdue University and Stanford University could have the potential to improve current hurricane prediction models and inform preparedness.

"We discovered that the dust optical depth is a key predictor of rainfall," says Zhu. "We found that while high dust density blocks radiation from the sun, cooling sea surface temperatures and weakening hurricane formation, low dust density can also enhance hurricane rainfall from nucleation processes"

The team developed a machine-learning model based on 19 years of data measuring hourly observed rainfall from satellites and other environmental variables. The new dust mechanism significantly improved the model prediction performance.

"It not only demonstrated an excellent prediction performance but also revealed multiple important physical mechanisms controlling the Atlantic hurricane rainfall, including Saharan dust," Zhu says.

Previous research by Zhu and his colleagues determined warming due to climate change would contribute to slower-moving hurricanes which would stall more frequently and lead to an increase in localized flooding. This new study provides new insight into other factors that could intensify flood potential.

"Scientists usually consider effects from ocean surface temperature and atmospheric moisture when studying hurricanes. Our study brings more attention to the question of how hurricanes interact with aerosols under changing climate," says Zhu. 

According to a recent report from NASA, “we may observe less Saharan dust, which may enhance hurricane rainfall along with the atmosphere's larger capacity to hold water vapor in the future warming climate."

Learn more about Zhu's research in the July 2024 cover story of the journal Science Advances.

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