Traffic-snarling, routine-ruining snowstorms are a fact of life in the eastern United States, but the region’s snowfall forecasts are notoriously difficult to make. This is partly because scientists don’t know much about what’s going on inside certain narrow ribbons of turbulent storm clouds, called “snow bands,” that can contain some of a storm’s heaviest snowfall rates.
Such areas of heavy precipitation can easily turn a carefully made snowfall forecast into a bust and unexpectedly paralyze highly populated regions, depending on their location and movement.
Now, NASA is gearing up to study East Coast snowstorms for the first time in 30 years. The agency’s latest airborne campaign, known as the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms, or IMPACTS, seeks to understand how small-scale snow bands form and evolve, and what’s happening inside them down to the level of individual ice crystals.
The data that is collected over the course of six weeks beginning Wednesday, and in subsequent field seasons in 2021 and 2022, will help scientists make sense of what satellites are seeing when they pass over winter storms.
If you live in the Washington metro area, “you know how bad the forecasts are,” said Gail Skofronick Jackson, the program manager for weather and atmospheric dynamics in NASA’s Earth Science Division. “This field campaign, IMPACTS, is going to provide information that’ll improve these models.”
To accomplish its mission, NASA will fly planes directly into the most turbulent areas of powerful snowstorms.
One of those planes, a P-3 Orion, will launch from Wallops Flight Facility in Virginia and aim to take measurements inside storm clouds. The other, a high-altitude ER-2 aircraft, will launch from an army base in Savannah, Ga., rendezvous with the P-3 and cruise above the cloud tops. Flying in a vertically stacked formation, the two planes will deploy a suite of instruments to investigate winter storms.
The P-3 will be outfitted with probes for determining the size, shape and concentration of cloud droplets, snow crystals and raindrops. Additional sensors will estimate the total amount of ice and liquid water present inside snowstorms and measure its isotopic composition to sleuth out its origin. If the planes are flying over the ocean, researchers will release small packages called dropsondes that measure weather conditions, including temperature, pressure, relative humidity, and wind speed and direction, all the way down to the surface.
Meanwhile, the ER-2, a civilian version of the U-2 spy plane, will be capturing a more zoomed-out picture of the storm. It will carry three radars and a lidar instrument to map snow-band structure, determine where snow is falling most intensely and build a picture of the storm’s wind field.
The ER-2 will also be carrying two radiometers, instruments that measure microwave radiation emitted by sources on Earth’s surface and in the atmosphere. When rain and snow are present in clouds, these radiometers see a slightly different signal than during clear conditions, and this can be used to estimate rain and snow amounts.
The radiometers are mission-critical because their measurements span the same wavelengths that NASA’s Global Precipitation Measurement satellite uses to detect snow and ice from space, said Lynn McMurdie, a research associate professor of atmospheric sciences at the University of Washington and principal investigator for IMPACTS. The information they collect will act as an independent check on the satellite, and it will help scientists improve the algorithms used to parse GPM data, which McMurdie said is used “for hundreds of applications.”
“The algorithms are very complicated black boxes that tease out what’s in the atmosphere,” McMurdie said. “And we need to perfect that black box.”
While the planes are in the air, crews from the University of Illinois at Urbana-Champaign and the State University of New York at Stony Brook will provide ground support, chasing storms that pop up in the Northeast and launching weather balloons when possible. The Stony Brook team will also deploy a truck-mounted radar, which it can use to rapidly scan storms as they roll ashore near Long Island.
NASA will also be coordinating with the National Weather Service, which will be ready to launch additional weather balloons at its request.
Stitching together all of the data from the two planes, ground crews and satellite overpasses will help scientists to “better characterize what’s happening in these storms,” Jackson said.
While this research could have the highly practical application of improving winter storm forecasts in the nation’s most densely populated region, it will also help address fundamental science questions, including why snow falls in concentrated bands in the first place.
“I can’t say with confidence today what makes those snow bands,” McMurdie said. “That’s what I hope to find out.”
The IMPACTS team, at the mercy of the forecast, will be checking the weather every day and making decisions several days out about where to send the planes. But the crews will be able to reach storms virtually anywhere on the Eastern Seaboard, as well as over parts of the Midwest.
Highest on the team’s wish list of storms to study is a nor’easter, a type of wintertime cyclone that forms off the Eastern Seaboard when mild maritime air collides with cold, dry air riding the polar jet stream out of Canada. These storms can dump feet of snow along the East Coast, pack hurricane-force winds and deliver major coastal flooding.
The NASA and university teams would be happy to study any and all snowstorms that pop up on their radar over the coming weeks.
“I’m just super excited about this field campaign,” Jackson said. “Let’s hope for snow.”