"Other studies have leaned the other way—that global warming by greenhouse gases makes hurricanes more intense and frequent," says Renyi Zhang.  "We found that aerosols may operate oppositely than greenhouse gases in terms of influencing hurricanes." (Credit: NASA Goddard Space Flight Center/Flickr)

Aerosols may sap hurricanes’ strength

Aerosols in the atmosphere tend to weaken the strength of hurricanes and tropical cyclones, contrary to what scientists previously believed.

For a new study, researchers used a complex computer model and data obtained from Hurricane Katrina to examine how aerosols produced by human activities, such as those from factories, power plants, car and airplane emissions, and other forms, play a role in the development of hurricanes.

Hurricane Katrina struck the Gulf Coast in 2005 and produced catastrophic damage.

The research also shows that aerosols tend to cause a hurricane to fall apart earlier. Wind speeds are lower than storms where anthropogenic aerosols are not present.

On average, there are about 90 hurricanes or cyclones that form each year around the world. The findings could be crucial in how destructive tropical storms are evaluated and prepared for.

“The results are surprising,” says Renyi Zhang, professor of atmospheric sciences at Texas A&M University, “because other studies have leaned the other way—that global warming by greenhouse gases makes hurricanes more intense and frequent. We found that aerosols may operate oppositely than greenhouse gases in terms of influencing hurricanes.

“Another thing we find, however, is that aerosols appear to increase the amount of precipitation in a hurricane or typhoon.  The rainbands associated with such tropical storms seem to be larger and stronger.”

Aerosol effect

Published in Nature Climate Change, the results could prove beneficial in how future hurricanes are studied—and how important the presence or absence of aerosols impact the development of such storms.

Katrina, for example, was the most destructive storm in US history, with damages totaling more than $100 billion. The storm killed more than 1,800 people. Winds topped 175 miles per hour and the storm flooded 80 percent of the New Orleans area.

“The information produced from this study could be very helpful in the way we forecast hurricanes,” Zhang says. “Future studies may need to factor in the aerosol effect. If a hurricane or typhoon is formed in a part of the world where we know that anthropogenic aerosols are almost certainly present, that data needs to be considered in the storm formation and development and eventual storm preparation.”

The study was funded by grants from NASA, Texas A&M’s Supercomputing facilities, and the Ministry of Science and Technology of China.

Source: Texas A&M University

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