Cyclone researchers: Global warming means more and more powerful Atlantic tropical storms

According to simulations using a high-resolution global climate model, a warming climate will increase the number and intensity of tropical cyclones in the North Atlantic, potentially creating more and stronger hurricanes.

“Unfortunately, this is not good news for people living in coastal areas,” said Christina Patrikola, an assistant professor of geological and atmospheric sciences at Iowa State University at the US Department of Environment’s Lawrence Berkeley National Laboratory. education. “In the future, Atlantic hurricane seasons will become more active and hurricanes will become more severe.”

The research team ran climate simulations using the Department of Energy’s Energy Exascale Earth System Model and found that the frequency of tropical cyclones during active hurricane seasons in the U.S. North Atlantic could increase by 66% by the end of this century. (These seasons are typically characterized by La Nina conditions – unusually cool surface waters in the eastern tropical Pacific – and a positive phase of the Atlantic Meridian Mode – warmer surface temperatures in the tropical north Atlantic).

The predicted number of tropical cyclones may increase by 34% during inactive North Atlantic hurricane seasons. (Inactive seasons typically occur during El Niño conditions, with warmer surface temperatures in the eastern tropical Pacific Ocean and cooler surface temperatures in the northern tropical Atlantic Ocean, with the negative phase of the Atlantic Meridian Mode.)

In addition, the simulations predict increased storm intensity during active and inactive storm seasons.

Scientific journal Geophysical Research Letters announced the results recently. Ana CT Sena, Postdoctoral Research Fellow at Iowa State, is the first author.

“Overall, a simultaneous increase in the number and strength (of tropical cyclones) could result in an increased risk to the continental North Atlantic in the future climate,” the researchers wrote.

Patricola added: “Anything that can be done to reduce greenhouse gas emissions can be helpful in reducing this risk.”

Cyclone studies in the land of cyclones

Iowa is home to the Cyclones, and storm sirens are part of the hype for most sporting events. We are talking about cyclones all over campus. What about North Atlantic tropical cyclones? What are they?

“Tropical cyclone is a more general term than hurricane,” Patricola said. “Hurricanes are relatively strong tropical cyclones.”

Exactly, says the National Oceanic and Atmospheric Administration. A tropical cyclone is a general reference to a low pressure system formed over tropical waters by thunderstorms near the center of a closed cyclonic wind. When these rotating winds exceed 39 mph, the system becomes a tropical storm. At speeds greater than 74 mph, it becomes a hurricane in the Atlantic and eastern Pacific Oceans, and a typhoon in the northwest Pacific Ocean.

Patricola grew up in the northeast and can still tell stories about Hurricane Bob in 1991.

“It was a big deal for us in Massachusetts,” he said. “For me it was very exciting. It really caught my interest.”

He was a Weather Channel fanatic during many hurricanes in the mid-1990s, and that led to research in geology and atmospheric sciences at Cornell University in New York, followed by research in atmospheric sciences and climate at Texas A&M University and Lawrence Berkeley National Laboratory. Patricola joined the faculty in August 2020 from Iowa State.

Patricola’s research interests include climate dynamics, climate variability and change, extreme weather events, atmosphere-ocean interactions, high-resolution climate modeling, land-atmosphere interactions, and paleoclimates. And tropical cyclones.

Why is the number of tropical cyclones so constant?

Patricola and another group of collaborators have just published their second tropical cyclone research paper. It’s also in Geophysical Research Letters, with postdoctoral research associate Derrick Danso of Iowa State as first author. The article examines a possible explanation for the relatively constant number of tropical cyclones observed around the world from year to year.

Could African Easterly Waves, low pressure systems that pick up moist tropical winds over the Sahelian region of North Africa and lift them into storm clouds, be the key to these persistently productive storms?

Using regional model simulations, the researchers were able to filter out the East African waves and see what happened. It turned out that the simulations did not change the seasonal number of Atlantic tropical cyclones. However, tropical cyclones were stronger, the peak of storm formation occurred between September and August, and the region of formation moved from the coast of North Africa to the Gulf of Mexico.

Thus, East African waves do not help researchers predict the number of Atlantic tropical cyclones each year, but they do affect important storm characteristics, including intensity and likely speed, where they make landfall.

Both documents require further investigation.

“We,” Patricola said, “solve the problem of predicting the number of tropical cyclones.”

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