Utah Researchers Shooting Snowflakes As They Fall

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utah snowflakesSnow enthusiasts have a long tradition of photographing snowflakes, going back nearly 100 years, when Wilson A. “Snowflake” Bentley spent hundreds of hours in a chilly barn in Jericho, Vermont, compiling about 5,000 photomicrographs.

But until a couple of years ago, there was no way to take 3-D pictures of free-falling snowflakes before they hit the ground. That’s when University of Utah researchers developed a digital camera system and installed it on the slopes of Alta, one of the snowiest ski areas in the country. The high-speed setup has enabled the scientists to significantly expand existing catalogs of snowflake images in a completely new way.

“We are photographing these snowflakes completely untouched by any device, as they exist naturally in the air,” said Tim Garrett, an associate professor of atmospheric sciences, adding that the unique camera device has captured about a half-million images so far. A gallery of flakes is online here, and you can watch flakes falling live atthis Alta Ski Area web page.

Improving forecasts
One of the big goals of the project is to improve weather forecasting by helping meteorologists identify how fast snowflakes are falling inside storm clouds.

“A lot of the difficulty is relating the radar reflections with actual precipitation…Right now we have weather models that provide forecasts for cold-weather storms, but we’ve experienced many times that the forecast can be a bit of a bust. That causes a lot of problems,” Garrett said. “The problem is that we do not have a very good sense for how the sizes and shapes of snow particles relate to how fast they fall.”

“The models are struggling with producing the right types of snow in the clouds…With different types of snow fall at different rates. If a storm make flakes that fall very quickly, it will fall farther upwind rather than downwind…If nothing else, we’d like to know when to go skiing,” Garrett said.

Weather models all over the world use formulas based on limited catalogs of about 100 snowflake types compiled in the Cascades back in the 1970s, he said, explaining that the data from the Alta project will help give forecasters a wealth of new information.

“These early researchers got only a few hundred images over two years because they had to collect each snowflake individually by hand,” Garrett said. “Our snowflake camera can automatically collect thousands of snowflake photographs in a single night.”

‘Beyond extraordinary’
“Something that we are seeing at Alta using the new camera is that the range of possible snowflakes falling out of the sky is beyond extraordinary. They are disimilar in ways that I could not have imagined before starting this project, and we are, perhaps, photographing these things for the first time and seeing all possible manifestations of the shapes in between,” he said.

“We want to characterize these things in a way that will lead to more accurate models,” he said, adding that having two cameras stacked vertically up the mountainside helps the researchers get a sense of the snowflakes change as they’re falling.

Along with the photos, a vertically pointing radar unit helps establish a profile of the depth and layers in the storm that provides context for the formation of the flakes, he explained.

Traditional snowflake photography tends to focus on particular types of crystals that lie flat on a microscope slide, “where a camera can get them perfectly in focus, and the photographer can take the time to get the light exactly right,” Garrett said.

“These perfectly symmetric, six-sided snowflakes, while beautiful, are exceedingly rare — perhaps one-in-a-thousand at the most. Snow is almost never a single, simple crystal. Rather, a snowflake might experience riming, where perhaps millions of water droplets collide with a snowflake and freeze on its surface. This makes a little ice pellet known as graupel. Or snowflakes collide with other snowflakes to make something fluffier, called an aggregate. And everything is possible in between.”

High-tech
NASA and the U.S. Army helped fund development of the camera, the National Science Foundation funded the observations, and Alta Ski Area has been helping with the setup and operation of the equipment.

The University of Utah’s Technology Commercialization Office helped Garrett and Cale Fallgatter — a 2008 master’s graduate in mechanical engineering — formed a spinoff company, Fallgatter Technologies, to make the new camera system, known as the MASC, for Multi-Angle Snowflake Camera, for which a patent is pending.

The device – under development for three years – includes three industrial-grade high-speed cameras: two 1.2-megapixel cameras and a 5-megapixel camera, plus two sets of two motion sensors to measure the speed of falling snowflakes. The 5-megapixel camera helps zoom in on single flakes, Fallgatter said.

The three cameras are mounted on a ring-shaped housing about 12 inches in diameter, with lenses pointing the center to capture the flakes as they fall through the ring. Motion sensors tell the cameras when to shoot, at a shutter speed of 1/25,000th to 1/40,000th and with three LED flashes, each equivalent to 40 watts, Fallgatter said. The multi-angle camera takes only black-and-white images because that gets more information; color filters block some light from images.

Greatest Snow on Earth
The cameras are set up on the slopes of storied Alta Ski Area. One is located at an elevation of 10,000 feet in Collins Gulch and the other at 8,500 feet at Alta Base.

“We can look at how the snowflakes change as they fall down the mountainside – if there is a change in the sizes and shapes of snowflakes as they fall,” Garrett said. “This is one of the things weather models try to simulate.”

Also at Alta Base, researcher Sandra Yuter of North Carolina State University operates a vertically pointing radar that measures the precipitation structure in the air column over Collins Gulch.

“The radar tells you how strong the storm is, where and when there are layers of rain and snow, and how tall the storm is,” Garrett says. “To interpret what we’re seeing with the cameras, it helps to know the structure within the storm and how it is changing with time.

“Ultimately, the primary diagnostic tool that weather forecasters use during a storm is radar, and they want to be able to relate what they see on radar to whether or not there is snow or graupel, and how much.”

The Alta Ski Area helps the project by providing a cabin for the instruments and a Snowflake Showcase through its website, where the public can see a live feed of Multi-Angle Snowflake Camera pictures. Daniel Howlett, an avalanche specialist with the Alta Ski Patrol, helps with camera installation, maintenance and data collection. Software for the snowflake camera was developed by Konstantin Shkurko, a University of Utah doctoral student in computer science.

In affiliation with Summit County Voice.

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