Wednesday, August 23, 2017
 
Barnes, Elizabeth

Barnes, Elizabeth

Questioning rivers in the sky

Thursday, June 1, 2017

As Edward Lorenz famously said in 1972, the flap of a butterfly’s wings in Brazil could spark a series of complex atmospheric events, eventually causing a tornado in Texas. But just as it would be impossible to know in advance the exact moment when a butterfly would flap its wings a thousand miles away, it is impossible to know of all the atmospheric complexities leading to a specific extreme weather event at a given time and place. Weather events like a tornado form rapidly and change quickly, and even the tiniest—seemingly insignificant—differences in the state of the atmosphere at a point in time will change the final outcome: when, where, or even if that tornado or extreme rain event will form.

Since the 1960s scientists have used the so-called "butterfly effect" to explain why we struggle to predict such extreme events with more than two weeks of advanced notice. But Elizabeth Barnes, Assistant Professor at Colorado State University, is pushing the envelope. Barnes likes making complex things simple, and with her team is turning the theory about Earth’s chaotic weather patterns on its head.

Barnes has been simplifying complicated problems her whole life. Before the atmosphere, it was particle physics.

“I was 12 years old, and I saw the movie Contact with Jodie Foster,” Barnes said. Foster plays an astrophysicist in the movie. “I decided I was going to be an astrophysicist, too, even though I didn’t know what a physicist was.”

As a physics and math major at the University of Minnesota, Barnes spent her college summers studying neutrinos (nearly massless, neutral particles produced from events like exploding stars) at a high-energy particle accelerator and detectors throughout the United States. It was then when she realized that as a particle physicist, she may spend her whole life simplifying and finding an answer to the single question of how neutrinos change as they travel. Instead, Barnes knew she wanted to ask lots of questions about the most complicated system she could think of, the Earth system, which involves complex interactions between many of our planet’s components such as the atmosphere, ocean, and land.

Barnes then decided to obtain a Ph.D. in atmospheric science at the University of Washington. “Ever since I’ve been playing with really interesting questions and seeing what the Earth can tell us about how it works,” Barnes said.

One of the questions she’s focused on these days is whether we can overcome the butterfly effect and make better predictions for atmospheric rivers. These “rivers” of tropical moisture get their name because, from a satellite view, they look like rivers of water flowing across the sky from the tropics to the mid-latitudes. Also, the heavy rain or snow they cause can seem like a river of water pouring from the sky when they make landfall on the west coast of North America. Both a blessing and a curse, atmospheric rivers provide the west coast with 30-50% of its annual precipitation, but they also cause damaging floods as seen in California in early 2017.

Because “upstream” atmospheric conditions can change so quickly, scientists struggle to predict atmospheric rivers beyond our current weather forecasting capability of 7-10 days. But Barnes is trying to push through the butterfly effect. She wants to determine whether we can skillfully predict atmospheric rivers multiple weeks in advance by looking for “teleconnections”—long distance relationships between the state of the atmosphere in one place and the state in another place hundreds or even thousands of miles away.

Barnes and her colleagues at Colorado State University are finding that the answer may lie in the tropical ocean. One pattern in the tropics, called the Madden-Julian Oscillation (MJO), is particularly promising. The MJO is a disturbance of clouds and rain that circles the world every 30 to 90 days, beginning in the Indian Ocean. This large cluster of thunderstorms moves through the atmosphere like a whale through the ocean, making waves that meteorologists call “Rossby waves.”

The exact location of the crests and troughs of these planet-spanning Rossby waves influence where and when heat and moisture move between the tropics and higher latitudes. When the MJO is in particular phases of its global trek, these Rossby waves can become nearly stationary, and the location of atmospheric high and low pressure systems can get stuck in a configuration that tends to block atmospheric rivers from making landfall in California. Instead, they are diverted towards the Gulf of Alaska.

“We have this whole arc of how that tropical information may tell us something about weather extremes due to atmospheric rivers hopefully beyond the 1-2 week weather timescale,” Barnes said.

Barnes is applying this research to her role as lead of the NOAA Subseasonal to Seasonal (S2S) Prediction Task Force. The goal of the S2S Prediction Task Force is to improve understanding and predictability of weather and climate phenomena falling within the 2 weeks to 2 months timescale. Past prediction efforts have mostly focused on forecasting either the weather timescale—days to 1-2 weeks in advance—or the seasonal climate timescale—2-3 months ahead. However, accurately forecasting the time range in between is key to allow emergency and reservoir managers to prepare for many different extreme events such as heat waves, hurricanes, and atmospheric rivers.

“In terms of the actual science happening [in the task force], it’s all over the board, which makes it really exciting every time you talk to anyone on the task force,” Barnes said. “They might be thinking about completely different science questions than you, but what links you is your timescale.”

Task force projects cover topics like the stratosphere, MJO, ocean circulations, tropical cyclones, drought, and land-atmosphere interactions. As the task force lead, Barnes’ is aiming to help the group leverage each member’s efforts and integrate their research towards a broader goal.

The task force is already starting to find ways to bridge the weather-climate gap, and they are just getting started. As for Barnes’ particular question, she is looking for more phenomena in the Earth system that may hold information to help with atmospheric river forecasting. She has many more questions to ask but is optimistic about the progress so far in pushing the envelope and moving beyond the butterfly effect.

“We can actually tell you something about atmospheric river activity three weeks from now,” she said. “That would have been absolutely baffling two decades ago.”

Barnes is supported by the NOAA Modeling, Analysis, Predictions, and Projections (MAPP) Program.

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