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SALT LAKE CITY — Most people already know that no two snowflakes are virtually the same, but a new study led by researchers at the University of Utah reveals how all these snowflakes are made. , and provides new insight into why it falls the way it does.
Their discovery is Published in the peer-reviewed scientific journal “Physics of Fluids” Last week, we noted that despite the “complexity of the snowflake’s structure and the heterogeneous nature of the turbulence,” the acceleration of the snowflake, and therefore the speed at which it falls, can be “uniquely determined” through a mathematical formula.
“This suggests that there is something very simple underlying the atmosphere, and we don’t really know what it is, but our results solve one of the most difficult aspects of atmospheric science. “It suggests that there may be a way to explain this in a certain way,” said Dr. Kremlin, professor of atmospheric sciences at the University of Utah and co-author of the study. said Tim Garrett, one of them.
This discovery could improve our understanding of snowstorms and avalanches and improve future predictions.
snowfall and movement
The results of this study were studied over a period of more than 10 years. When Garrett decided to dig deeper into the problem, he began measuring how fast snowflakes fall at Alta. He thought this was a perfect topic to explore, given his interest in the physics of motion and the fact that Utahns generally love to talk about snow. .
This led to early observations that snowflakes did not fall as expected based on traditional weather and climate models, which were essentially based on equipment that only considered snow falling in still air. Snow falls in a much more unique way than the models suggest, but this wasn’t all that surprising.
“Atmospheric scientists don’t admit it, but of course everyone knows that snowflakes swirl in the air,” he told KSL.com, recalling the moment. .
So he enlisted the help of researchers Dheeraj Singh and Eric Pardijak from the university’s School of Mechanical Engineering to help solve the relationship between snowfall and atmospheric turbulence. They invented and patented a device called. Differential emissivity imaging disdrometer To solve this scientific mystery, we measure the mass, size, and density of snowflakes.
With the help of a National Science Foundation grant, the team installed the device at the Little Cottonwood Canyon site during the 2020-2021 winter season. They studied temperature, relative humidity, turbulence, and other weather factors, and analyzed more than 500,000 individual snowflakes. All this information provides a “comprehensive picture” that has never been seen before, Garrett said.
What they discovered when they put all this information together was that they could use the Stokes number of a flake to predict how quickly snow would fall. The Stokes number is a dimensionless number that helps scientists understand how particles respond to changes in flow, such as air turbulence. Typically, the Stokes number is higher when it rains and lower when it snows. This is why the Stokes number declines in very different ways.
“As a result, snow tends to be blown away by turbulence, while rain tends to fall straight through turbulence,” Garrett said. “What we ended up discovering was that if you knew the Stokes number, this one dimensionless number, in a sense, our snowflake world was our oyster. “This was enough information to explain how often snowflakes have a certain level of acceleration.” ”
The researchers also cited previous research from decades ago that suggests cloud updrafts influence snowflake formation. Adding new knowledge means it may be possible to completely determine snowfall by measuring cloud turbulence, Garrett explained.
why is it important
This could have several implications going forward. For example, how snowflakes fall is considered a “key parameter” for predicting weather, Garrett said, adding that traditionally the rate at which moisture falls from clouds depends on how long a storm lasts. This is because it is a measure of whether it will continue, the company said in a statement prior to the study’s publication.
He told KSL.com that while the study “doesn’t provide immediate answers” about how to better predict storm length and strength, it could provide new insights into the relationship between snowfall and wind. It was clearly stated that there is a sex. It could lead to breakthroughs in meteorology in the future.
“If we can show in the future that that’s the case and that this is indeed supported, that could lead to some pretty significant improvements in storm modeling,” he said. “One of the biggest challenges weather models currently have is predicting the types of snowflakes that form in clouds. Our results show that despite some difficulties, It suggests that it could become something (less complex).”
In the end, it could just be measuring the movement of air in clouds.
Meanwhile, the tool that led to this discovery, the differential emissivity imaging disdrometer, is already being used in other influential ways. The Utah Department of Transportation has purchased several pieces of equipment to help predict avalanches in places like Little Cottonwood Canyon. This is because it instantly measures snow density, which is often a factor in avalanches.
The work isn’t finished. Garrett says he and his colleagues have collected more data than they will likely have time to decipher. But he plans to continue to scrutinize it and run experiments to better understand snowfall.
And as he and others unravel the mysteries of snow, he hopes everyone can find the beauty in the way snowflakes fall in the air this winter.