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Kevin Reed

Xiaoning Wu at her recent PhD graduation with Kevin Reed. Photo by Gordon Taylor

By Daniel Dunaief

If they build it, they will understand the hurricanes that will come.

That’s the theory behind the climate model Kevin Reed, Associate Professor at the School of Marine and Atmospheric Sciences at Stony Brook University, and his graduate student Xiaoning Wu, recently created.

Working with Associate Professor Christopher Wolfe at Stony Brook and National Center for Atmospheric Research scientists, Reed and Wu developed an idealized computer model of the interaction between the oceans and the atmosphere that they hope will, before long, allow them to study weather events such as tropical cyclones, also known as hurricanes.

In his idealized program, Reed is trying to reduce the complexity of models to create a system that doesn’t require as much bandwidth and that can offer directional cues about coming climate change.

“When you’re trying to build a climate model that can accurately project the future, you’re trying to include every process you know is important in the Earth’s system,” Reed said. These programs “can’t be run” with university computers and have to tap into some of the biggest supercomputers in the world.

Reed’s work is designed to “peel back some of these advances that have happened in the field” which will allow him to focus on understanding the connections and processes, particularly between the ocean and the atmosphere. He uses fewer components in his model, reducing the number of equations he uses to represent variables like clouds.

“We see if we can understand the processes, as opposed to understanding the most accurate” representations possible, he said. In the last ten years or so, he took a million lines of code in a climate model and reduced it to 200 lines.

Another way to develop a simpler model is to reduce the complexity of the climate system itself. One way to reduce that is to scale back on the land in the model, making the world look much more like something out of the 1995 Kevin Costner film “Waterworld.”

About 30 percent of the world is covered by land, which has a variety of properties.

In one of the simulations, Reed reduced the complexity of the system by getting rid of the land completely, creating a covered aqua planet, explaining that they are trying to develop a tool that looks somewhat like the Earth.

“If we could understand and quantify that [idealized system], we could develop other ways to look at the real world,” he said.

The amount of energy from the sun remains the same, as do the processes of representing oceans, atmospheres and clouds.

In another version of the model, Reed and Wu represented continents as a single, north-south ribbon strip of land, which is enough to change the ocean flow and to create currents like the Gulf Stream.

The expectation and preliminary research shows that “we should have tropical cyclones popping up in these idealized models,” Reed said. By studying the hurricanes in this model, these Stony Brook scientists can understand how these storms affect the movement of heat from around the equator towards the poles.

The weather patterns in regions further from the poles, like Long Island, come from the flow of heat that starts at the equator and moves to colder regions.

Atlantic hurricanes, which pick up their energy from the warmer waters near Africa and the southern North Atlantic, transfer some of that heat. Over the course of decades, the cycling of that energy, which also reduces the temperature of the warmer oceans, affects models for future storm systems, according to previous studies.

Reed said the scientific community has a wide range of estimates for the effect of hurricanes on energy transport, with some researchers estimating that it’s negligible, while others believing it’s close to 50 percent, which would mean that hurricanes could “play an active role in defining” the climate.

Reed’s hypothesis is that a more rapid warming of the poles will create less of an energy imbalance, which will mean fewer hurricanes. This might differ in various ocean basins. He has been studying the factors that control the number of tropical cyclones.

Reed and Wu’s research was published in the Journal of Advances in Modeling Earth Systems in April.

Wu, who is completing her PhD this summer after five years at Stony Brook, described the model as a major part of her thesis work. She is pleased with the work, which addresses the changing ocean as the “elephant in the room.”

Oftentimes, she said, models focus on the atmosphere without including uncertainties that come from oceans, which provide feedback through hurricanes and larger scale climate events.

Wu started working on the model in the summer of 2019, which involved considerable coding work. She hopes the model will “be used more widely” by the scientific community, as other researchers explore a range of questions about the interaction among various systems.

Wu doesn’t see the model as a crystal ball so much as a magnifying glass that can help clarify what is happening and also might occur in the future.

“We can focus on particular players in the system,” she said.

A native of central China, Wu said the flooding of the Yangtze River in 1998 likely affected her interest in science and weather, as the factors that led to this phenomenon occurred thousands of miles away.

As for her future, Wu is intrigued by the potential to connect models like the one she helped develop with applications for decision making in risk management.

The range of work she has done has enabled her to look at the atmosphere and physical oceanography and computational and science communication, all of which have been “useful for developing my career.”

Kevin Reed. Photo from SBU

By Daniel Dunaief

At the beginning of this month, the North Atlantic started its annual hurricane season that will extend through the end of November.

Each year, the National Oceanic and Atmospheric Administration offers a forecast in May for the coming season. This year, NOAA’s Climate Prediction Center anticipates a 60 percent chance of an above-normal season. The Center anticipates 13 to 19 storms, although that number doesn’t indicate how many storms will make landfall.

These predictions have become the crystal ball through which forecasters and city planners prepare for a season that involves tracking disturbances that typically begin off the West coast of Africa and pick up energy and size as they travel west across the Atlantic towards Central America. While some storms travel back out to sea, others threaten landfall by moving up the Gulf Coast or along Atlantic Seaboard of the United States.

Kevin Reed, an Associate Professor at Stony Brook University’s School of Marine and Atmospheric Sciences, and Alyssa Stansfield, a graduate student in his lab, recently predicted the likely amount of rainfall from tropical cyclones.

Alyssa Stansfield at the 33rd Conference on Hurricanes and Tropical Meteorology in 2018. Photo by Arianna Varuolo-Clarke

 

Using climate change projection simulations, Reed and Stansfield came up with a good-news, bad-news scenario for the years 2070 through 2100. The good news in research they published in Geophysical Research Letters is they anticipate fewer hurricanes.

The bad news? The storms will likely have higher amounts of rain, with increased rain per hour.

“If you focus on storms that make landfall over the Eastern United States, they are more impactful from a rainfall standpoint,” Reed said. “The amount of rainfall per hour and the rainfall impact per year is expected to increase significantly in the future.”

In total, the amount of rainfall will be less because of the lower number of storms, although the intensity and overall precipitation will be sufficient to cause damaging rains and flooding.

Warmer oceans and the air above them will drive the increased rainfall, as these storms pass over higher sea surface temperatures where they can gain energy. Warmer, moist air gives the hurricanes more moisture to work with and therefore more potential rainfall.

“As the air gets warmer, it can hold more water in it,” Stansfield said. “There’s more potential rain in the air for the hurricanes before they make landfall.”

Stansfield said the predictions are consistent with what climatologists would expect, reflecting how the models line up with the theory behind them. She explored how climate change affects the size of storms in this paper, but she wants to do more research looking at hurricane size in the future.

“If hurricanes are larger, they will drop rainfall over a larger area,” which could increase the range of area over which policy makers might need to prepare for potential damage from flooding and high winds, Stansfield said.

While her models suggest that storms will be larger, she cautioned that the field hasn’t reached a consensus about the size of future storms. As for areas where there is greater consensus, such as the increased rainfall their models predict for storms at the end of the century, Stansfield suggested that the confidence in the community about their forecasts, which use different climate models, is becoming “more apparent as more modeling groups reach the same conclusion.”

Alyssa Stansfield at Sequoia National Park in 2018. Photo by Jess Stansfield

In explaining the expectations for higher rainfall in future storms, Reed said that even storms that had the same intensity as current hurricanes would have an increase in precipitation because of the availability of more moisture at the surface.

While storms in recent years, such as Hurricanes Harvey, Florence and Dorian dumped considerable rain in their path because they moved more slowly, effectively dumping rain over a longer period of time in any one area, it’s “unclear” whether future storms would move more slowly or stall over land.

Several factors might contribute to a decrease in the number of storms. For starters, an increase in wind sheer could disrupt the formation of some storms. Vertical wind sheer is caused when wind speed and direction changes with increasing altitude. Pre-hurricane conditions may also change due to internal variability and the randomness of the atmosphere, according to Reed.

Reed said the team chose to use climate models to make predictions for the end of the century because it is common in climate science for comparison to the recent historical record. They also used a 30 year period to limit some of the uncertainty due to internal variability of weather systems.

Stansfield, who is in her third year of graduate school and anticipates spending another two years at Stony Brook University before defending her graduate thesis, said she became interested in studying hurricanes in part because of the effects of Superstorm Sandy in 2012.

Alyssa Stansfield at Yosemite in 2019. Photo by Kathy Stansfield

When she was younger, she and her father Greg used to go to the beach when a hurricane passed hundreds of miles off the coast, where she would see the impact of the storm in larger waves. At some point, she would like to fly in a hurricane hunter plane, traveling directly into a storm to track its speed and direction.

Stansfield said one of the more common misconceptions about hurricanes is that the category somehow determines their destructive power. Indeed, Superstorm Sandy was a Category 1 hurricane when it hit New York and yet it caused $65 billion in damage, making it the 4th costliest hurricane in the United States, according to the NOAA.

After Stansfield earns her PhD, she said she wants to continue studying hurricanes. One question that she’d like to address at some point is why there are between 80 to 90 hurricanes around the world each year. This has been the case for about 50 years, since satellite records began.

“That’s consistent every year,” she said. “We don’t know why that’s the number. There’s no theory behind it.” She suggested that was a “central question” that is unanswered in her field. 

Understanding what controls the number of hurricanes will inform predictions about how that number will change in response to climate change.