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Tuesday, February 27, 2024

Scientists Chase Snowflakes During the Warmest Winter Ever

Inside a cavernous hangar at NASA’s Wallops Flight Facility along the Virginia coast, a gleaming white P-3 Orion aircraft sits parked under harsh floodlights. It’s just after midnight and a group of scientists, technicians and graduate students cluster underneath a wing, peering at a 5-inch crack in one of the ailerons that the pilot uses to maneuver the plane.

Their disappointment is palpable. The eight-person team was preparing to board the research aircraft for a 10-hour flight through a massive snowstorm stretching across upstate New York and Canada as part of a new project funded by NASA to dissect the inner workings of winter storms. The researchers want to know how the bands of snow form, why some storms produce snow and others don’t, and why certain conditions lead to ice crystals, while others cause snowflakes. Their ultimate goal is better winter forecasts for the 55 million residents of the Northeast, and improved weather models that can be used for the rest of the US. NASA has dubbed the three-year study IMPACTS, or the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms.

But tonight’s scientific expedition into the heart of the storm is now canceled. The crack—possibly caused by hitting a bird or other object on the previous flight—will take a few days to repair. It takes a few minutes to sink in, but after a few glum jokes about the bird, the team shuffles out of the hangar and into two windowless rooms, plugs in their laptops and readies for a night of number-crunching data from satellites and a second aircraft, instead.

Lynn McMurdie, principal investigator for the project and an atmospheric scientist at the University of Washington, spent several years assembling her research team from universities and NASA’s Goddard Space Flight Center. She won a competitive NASA grant and moved her lab to the remote Wallops Flight Facility near Chincoteague Island, Virginia. Imagine being a scientist who studies snowstorms and your project kicks off during one of the warmest winters on record. Then the plane breaks.

“It has made us all frustrated,” says McMurdie. “That’s one thing about an airborne mission: We can go where airplanes go and we go where there are storms. Even if it’s raining at the surface, it’s different above. So we have been able to make lemonade out of lemons.”

Not counting this night’s grounded flight, McMurdie and colleagues have flown on 12 trips since the beginning of January. While that may seem like a lot, it's actually about half of what they expected. There just haven’t been very many storms this year. NOAA officials say the 2019-2020 winter, which officially stretches from December to February, is on track to be one of the warmest ever, although the amount of snowfall has varied by region. The Eastern United States is lining up to have the one of the top 10 least snowy winters in the past 126 years, according to a database maintained by Rutgers University. Bostonians tied for their warmest winter on record with an average temperature of 37.9 degrees Fahrenheit. New York’s Central Park has only measured a total of 4.8 inches of snow this winter, just over a foot below the average to date, and its second least-snowy season since records began in 1868. This year, there have been no winter storm warnings for a number of East Coast cities including New York, Cincinnati, Baltimore, Washington D.C. and Pittsburgh.

“The surprising thing is we have gotten fantastic data, despite that,” McMurtie says. “We still have recorded snowstorms. They are just not frequent as expected and not as widespread. We are still learning about the structure of the storms. By making these cloud measurements, it helps us with our forecasting models, and the hope is to improve our forecasting of snowfall on the ground.”

McMurdie says the data she and her colleagues are collecting will also probe scientific mysteries about snowstorms. “One of the main things we are investigating is why some winter storms are very snowy and some are not,” she says. “We are investigating why snow is distributed the way it is. Usually it is organized in banded structures. You would see a swath of clouds from Florida to Maine. But within the clouds, snow is not continuous, it is in these narrow banded regions.”

Even though the P-3 Orion is grounded, the scientific team is banking on another aircraft to collect data tonight, a high-altitude ER-2 from Hunter Army Airfield in Savannah, Georgia. As the team watches on a massive computer monitor, the lone pilot takes off around 1 a.m. and reaches an altitude of 65,000 feet in about 20 minutes. He flies up to Lake Ontario, across to Quebec, and then follows a back-and-forth “mowing the grass” pattern down to Pennsylvania using instruments that scan the tops of storm clouds.

The ER-2 aircraft carries six different types of radar, lidar, and microwave instruments, all tuned to different frequencies ideal for gathering snow measurements remotely. In contrast, the P-3 is designed to fly right through the snowstorm to sample snow, ice, humidity and temperature. As they track the plane from the ground station at Wallops, several researchers compare the ER-2 data to satellite imagery to get an idea of what’s happening at the upper level of the storm.

Greg Sova wants to know what’s happening lower down, in the heart of the storm. For the past two months, Sova, a graduate student at the University of North Dakota, has been collecting data from a cloud particle imager, a gold-colored instrument affixed under the wing of the P-3 aircraft. A laser beam flows between twin prongs of the torpedo-shaped imager. The device records images of microscopic snowflakes as they pass through the light beam and cast a shadow on a detector.

Sova then sorts the snowflake into recognizable categories. “You can tell by the shape of the snowflake at which temperature and how high in the atmosphere the snow is developing,” says Sova. He’s collected hundreds of snowflake pictures on his laptop. Some look like the traditional six-armed crystal you drew back in nursery school, which is technically known as a dendrite. Others look like spiky sticks with blobs on the ends. These are called capped columns. Still others take the form of symmetrical hexagonal shapes connected by a blob in the middle; these Sova likens to the Imperial TIE fighters from Star Wars.

“The images help get a better understanding of what the snow growth is inside the clouds,” says Sova. “Our current way of measuring snow happens from satellites in space or on the ground. As to what’s happening inside the cloud itself, we have to make educated guesses.”

A few cubicles away from Sova, another scientist who was planning to fly tonight is instead watching a bank of computer monitors displaying colorful satellite imagery. Joe Finlon, a University of Washington postdoctoral student in meteorology, has been watching upper cloud formation. He’s found some wiggles in the satellite images taken around Oswego, New York, that he says might reflect the effects of gravity waves through the storm.

The atmosphere around a storm behaves like a tempestuous ocean, with warm air rising and waves of cold air falling. Heavy waves of moisture-laden air rise and then sink due to the effects of gravity within a stable layer of the atmosphere. That can cause a big dump of snow in a small area, while leaving none around it. Gravity waves in snowstorms are a relatively recent discovery and not easy to find or forecast, so this rarely-seen phenomena has him pretty excited. “This is something unique we haven’t seen often in a storm this year,” Finlon says.

It’s now nearly 8 a.m., and after staying up all night, the team is still collecting data from the ER-2 flight and orbiting weather satellites. The storm has dumped up to six inches across parts of New York and parts of New England, delighting skiers who have been starved of snow, while frustrating commuters preparing for their morning drives.

Of course, many winter-lovers want to know what the future holds, and the prospect of doing snowstorm research during the warmest winter yet along the Eastern seaboard raises some tantalizing questions about whether this is becoming the new normal. But IMPACTS isn’t actually designed to study long-term climate change; the data it collects only gives clues to the frequency and strength of snowstorms. And so far, researchers haven’t conclusively figured out how climate change will affect future snowfall totals.

Because there’s a big natural seasonal variability in the amount of snow that falls in a given location, it’s hard to tease out how climate change will push it one way or another. In fact, a warming climate will have conflicting effects on Eastern snowfall, says Colin Zarzycki, assistant professor of meteorology and climate dynamics at Pennsylvania State University, who is not involved in the IMPACTS study.

“On one side, the obvious or natural conclusion is that as the atmosphere warms, we expect a reduced frequency of snowstorms,” Zarzycki says. “But the level of water vapor available to fall out of a storm as precipitation increases as climate warms as well. We will have a bigger sponge that is tracking along the East Coast. When it’s time to wring it out, we have more liquid. If it’s cold enough at the surface, it can fall as snow.”

Overall, Zarzycki predicts fewer, but bigger, snowstorms in the future. “Instead of getting six or seven mini-storms each year, we only get two or three. But we get one or two of these big Twitter-hashtag storms,” he says referring to storms that collect names like #Snowzilla or #Snowmegeddon or #Snowpocalypse.

For McMurdie and the other IMPACT researchers, even a little bit of snow and some more data to compile would make them happy. After tonight, their flights are done for the winter. The team will pack up and return home, convening over the summer to compare datasets and prepare for the 2020-21 field season.

“I’m not depressed,” McMurdie says with a chuckle. “I’ve got two more years.”

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