NASA Scientist Develops First 3D Model of Melting Snowflake
NASA is set to launch two satellite missions this year, in addition to conducting field research that will give scientists a better view of Earth’s frozen regions – made up of glaciers, ice sheets, permafrost, sea ice, and snow cover – known collectively as the cryosphere.
One of the ways NASA studies the cryosphere is through snowflake research – particularly how snow melts. With a better understanding of melting snow, scientists can learn to improve prediction science by recognizing the signature in radar signals of wet, heavy snow, the type of precipitation that can lead to broken tree limbs and power lines.
A newly released video, developed by Jussi Leinonen of NASA’s Jet Propulsion Laboratory (JPL) in California, visualizes the first 3D numerical model of snowflakes actively melting in the atmosphere. It’s the first study that simulates the melting of snowflakes in 3D by replicating the physical processes on a computer.
Leinonen’s model reproduces key features of melting snowflakes that have been observed in nature. First, meltwater gathers in any concave regions of the snowflake’s surface. These liquid-water regions then merge to form a shell of liquid around an ice core, and finally develop into a water drop. The modeled snowflake shown in the video is less than half an inch (one centimeter) long and composed of many individual ice crystals whose arms became entangled when they collided in midair.
Leinonen said he got interested in modeling melting snow because of the way it affects observations with remote sensing instruments. A radar “profile” of the atmosphere from top to bottom shows a very bright, prominent layer at the altitude where falling snow and hail melt — much brighter than atmospheric layers above and below it. “The reasons for this layer are still not particularly clear, and there has been a bit of debate in the community,” Leinonen said.Simpler models can reproduce the bright melt layer, but a more detailed model like this one can help scientists to understand it better, particularly how the layer is related to both the type of melting snow and the radar wavelengths used to observe it.
As the 3D simulation shows, meltwater will first gather on the surface of a snowflake in concave, liquid-water regions. Then, the regions will merge together and form a liquid shell around an ice core, before finally turning into a water droplet. The one-centimeter-long 3D snowflake model in the video is made up of many individual ice crystals. When they collide in midair, the crystals’ arms get tangled together.
In a top to bottom atmospheric radar profile, a prominent, extremely bright layer – far brighter than surrounding atmospheric layers – is visible at the altitude where falling hail and snow melt.
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