When the temperature drops to 32 degrees Fahrenheit, one can expect that precipitation will fall in the form of snow. But sometimes, due to a variety of specific weather conditions, it doesn’t.
Leaders of a project called “Mountain Rain or Snow” are asking Vermonters to report what type of precipitation is falling in different locations around the state. The results could help scientists with groups like the National Aeronautics and Space Administration better understand how to monitor the water cycle.
About 60 years ago, while members of the U.S. Corps of Army Engineers studied rain and snow in the Sierras, they noticed snow falling when the air temperature remained above freezing.
That contradicted the assumption used in different types of modeling — from weather models to climate and hydrologic models — that snow falls when the air temperature drops to 32 F.
“That turned out to cause a bunch of problems, because it actually snows at warmer temperatures than that, and conversely — and somewhat less frequently — we can get rain when it’s below freezing at the land surface,” said Keith Jennings, a water resources scientist for Lynker, a Colorado-based consulting group that’s leading the project.
The project is funded by NASA’s Citizen Science for Earth Systems Program. Lynker partners with groups like the National Oceanic and Atmospheric Administration and the Desert Research Institute, a nonprofit research group connected to the Nevada System of Higher Education.
“If you’re out hiking in the mountains and it’s raining at the trailhead, but snowing on the summit of Camel’s Hump, or if you’re heading up the chairlift — all of that information, all those data points are super valuable,” he said. “Hopefully that’ll let us improve satellite data products that we have from NASA, or improve weather forecasts, or improve the way we represent rain and snow in water resources models.”
Using an app developed for the project, Jennings is hoping that people who live across the region — in Vermont, New Hampshire and parts of New York — will report the weather conditions outside “whenever they can, as often as possible,” he said.
While one monitoring station already exists at Burlington International Airport, Jennings said the project needs people from around Vermont to “fill in the gaps.”
Around 200 citizen scientists in the Sierra Nevada region contributed to a nearly identical project by the same group, which led to a study last February in the journal Frontiers in Earth Science.
Participants reported that, most of the time, snow — not rain — fell in temperatures between 32 F and 39.5 F, showing the temperature threshold for snow is likely different than scientists long have thought.
Western Nevada and eastern California are, hydrologically, much different than Vermont, Jennings said, which is why the project is now focusing efforts on the Northeast.
“The initial data and some of the other data sets we’ve worked with have suggested that those patterns can actually be quite different depending on where you are,” he said. “The Colorado Rocky Mountains — we could get snow up to 40 degrees Fahrenheit there, whereas if you’re in Vermont, if it’s 40 degrees, it’s almost always going to be rainfall.”
Because the project is government-funded, all of its data will be publicly available “so that anybody who’s interested in working with these data, whether they’re a researcher, whether they’re a water resources manager at a municipality or water utility, or if it’s just a curious amateur scientist” can download them, Jennings said.
As global temperatures warm, part of the group’s motivation is “monitoring snow that we get while we have it” to help accurately analyze historical trends, Jennings said.
“Even though this isn’t a climate-change-specific project, our hope is that we’ll be able to find patterns and relationships that we can use for climate change analysis as well,” he said.
Anyone interested can learn more about participating at rainorsnow.org.
