Featured Research

from universities, journals, and other organizations

Why it snows so much in the frozen north

Date:
December 20, 2013
Source:
Michigan Technological University
Summary:
Scientists have long puzzled over the seemingly ceaseless drizzle of snow drifting down from arctic clouds. Now they may have an explanation.

Atmospheric particles that were previously thought to be useless for making ice crystals may be the driver of arctic snows, say Michigan Tech scientists. These ominous clouds above the Arctic Ocean were photographed north of Russia.
Credit: NOAA Climate Program Office, NABOS 2006 Expedition

When it doesn't show signs of stopping, most of us just mumble a few choice words and get out the snow shovel. Scientists, however, wonder where all that snow is coming from, particularly in pristine places like the Arctic. Raymond Shaw and his colleagues may have found an answer.

Here's the conundrum: Snow doesn't just materialize out of thin air. For those delicate, six-sided crystals of ice to form, they need a nucleus, a speck of dust, where water molecules can cling and order their structure as they freeze. Those ice-forming nuclei are relatively rare. Yet, over the Arctic, where the atmosphere is very clean and the ocean is covered with ice, sometimes it snows interminably. With bazillions of snowflakes crystalizing over dust specks and falling to Earth, why don't the clouds run out of nuclei? And why doesn't it quit snowing?

The same question applies to a lesser degree in places like Lake Superior, whose soggy clouds drop countless megatons of snow on the hapless residents of Minnesota, Wisconsin and Michigan.

"Within a few hours, you basically purge the atmosphere of all those particles," said Shaw, a physicist at Michigan Technological University. "So how can it snow for days on end?"

To answer the question, Shaw and his colleagues, including graduate student Fan Yang, set about developing a model to describe how ice crystals form, grow and fall, and they backed it up using data on arctic clouds, which are very well studied. They hoped that by characterizing just how snow comes into being, they would uncover clues to the puzzle.

What they discovered surprised them. As the number of snow crystals increases, their mass soars by a power of 2.5. "Our first guess would have been that if you triple the number of crystals, you triple the mass," said Shaw. "It turns out to be a much stronger relationship than that." For example, if you triple the number of crystals, the mass goes up by a factor of 16. Simply put, the more crystals you have, the bigger they are.

Their model hinges on the idea that ice crystals are forming on atmospheric particles that were previously thought to be useless for making ice crystals. "The key assumption we made was that there's a hidden source of ice nuclei that's always there, but they are just really, really low efficiency," said Shaw. "The consensus in the research community has been that you need special pieces of dust to catalyze the ice. We thought, 'What if there was more stuff out there that would produce ice if you just wait long enough? Maybe when you put it in contact with a drop of water, it doesn't freeze immediately. But if you wait an hour, or two hours, it does. Our model assumes that the atmosphere is full of those really inefficient nuclei."

Those inefficient nuclei are behind those big crystals that show up during heavy snowfalls.

"The mass of an ice crystal is related to its growth time," Shaw said. "The longer it's in the cloud, the bigger it will be." So, when there's an updraft that keeps crystals from falling, snowflakes that form on regular, snow-forming particles get larger and larger. During that time, many more snowflakes have a chance to form on weak nuclei.

Eventually, all the snow crystals get too heavy for the updraft to support, and they tumble earthward. By then, they are huge, and there are lots of them. Not only is that born out in Shaw's model, it also appears to fit with data gathered from arctic clouds.

They don't know what those weak nuclei are, or where they come from. But the scientists on Shaw's team are confident enough in their existence that they are looking for them in lab experiments.

"By assuming they are there, we got this mathematical prediction that fits with the experimental data," said Shaw. "So there's indirect evidence that these inefficient nuclei are there. This could be a solution to the mystery."

The study was funded by the US Department of Energy. An article describing their work, "A Minimalist Approach to Modeling Complex Arctic Clouds," coauthored by Shaw, Yang and Mikhail Ovchinnikov, a research scientist at Pacific Northwest National Laboratory, was published in the July 2013 edition of Geophysical Research Letters.


Story Source:

The above story is based on materials provided by Michigan Technological University. The original article was written by Marcia Goodrich. Note: Materials may be edited for content and length.


Journal Reference:

  1. Fan Yang, Mikhail Ovchinnikov, Raymond A. Shaw. Minimalist model of ice microphysics in mixed-phase stratiform clouds. Geophysical Research Letters, 2013; 40 (14): 3756 DOI: 10.1002/grl.50700

Cite This Page:

Michigan Technological University. "Why it snows so much in the frozen north." ScienceDaily. ScienceDaily, 20 December 2013. <www.sciencedaily.com/releases/2013/12/131220200657.htm>.
Michigan Technological University. (2013, December 20). Why it snows so much in the frozen north. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2013/12/131220200657.htm
Michigan Technological University. "Why it snows so much in the frozen north." ScienceDaily. www.sciencedaily.com/releases/2013/12/131220200657.htm (accessed July 28, 2014).

Share This




More Earth & Climate News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Carbon Trap: US Exports Global Warming

The Carbon Trap: US Exports Global Warming

AP (July 28, 2014) AP Investigation: As the Obama administration weans the country off dirty fuels, energy companies are ramping-up overseas coal exports at a heavy price. (July 28) Video provided by AP
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Trees Could Save More Than 850 Lives Each Year

Trees Could Save More Than 850 Lives Each Year

Newsy (July 27, 2014) A national study conducted by the USDA Forest Service found that trees collectively save more than 850 lives on an annual basis. Video provided by Newsy
Powered by NewsLook.com
Phoenix Thunderstorm Creates Giant Wall of Dust

Phoenix Thunderstorm Creates Giant Wall of Dust

Reuters - US Online Video (July 26, 2014) A giant wall of dust slowly moves north over the Phoenix area after a summer monsoon thunderstorm. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins