February 19, 2013
Topography Around Lakes Can Influence Lake-Effect Snow Events
Brett Smith for redOrbit.com - Your Universe Online
People living around the Great Lakes and near the Great Salt Lake know all about how lake-effect snow bands can move in quickly and dump several inches of the white stuff in just a few hours.
A pair of Utah researchers has found the topography around a lake can greatly influence the amount and range of a lake-effect snow event, according to a new study in the new journal Monthly Weather Review.
The study's senior author, Jim Steenburgh, a professor of atmospheric sciences at the University of Utah, said his team´s findings could refine predictions for lake-effect snow storms, which often slow traffic to a crawl and close schools.
"It is going to help us with weather prediction — helping forecasters recognize that in some lake-effect events, the mountains or hills can play an important role in triggering lake-effect snow bands" over large bodies of water, he said.
Lake-effect snow occurs when a cold mass of air passes over a large body of warmer water. The air picks up moisture and heat, making it rise. When the air mass reaches a certain altitude, it cools – resulting in a downwind snowfall.
Meteorologists have known for some time lake-effect snowfall increases as warm, moist air rises over mountains. However, the new study shows something different: mountains themselves can influence the lake-effect over the body of water itself.
Using existing weather data and weather modeling software, Steenburgh and Trevor Alcott, who is currently working at the National Weather Service in Salt Lake City, created a computer simulation that closely mimics an actual lake-effect storm from Oct. 26 and 27, 2010. The computer model allowed the researchers to incorporate the effects of the Great Salt Lake and surrounding topography by running the simulation multiple times, but with various aspects missing.
"We can play God with this model," Steenburgh said. "We can see what happens if the upstream terrain wasn't there, if the lake wasn't there, if the Wasatch Range wasn't there."
They found the Wasatch and Oquirrh ranges effectively funnel air south, over the Great Salt Lake, and into the valley further to the south. This convergence of air amplifies the lake-effect snowfall.
The air flow also rises as it cools, drawing land breezes onto the lake from its western and eastern shores. The converging airflow results in the formation of lake-effect snow bands directly over the lake.
"There is a rich spectrum of lake-effect snowstorms," Steenburgh said. "Some cover a wide area with light snowfall. Some organize into more intense snow bands that produce heavier snow over a smaller area. Over the Great Salt Lake, 20 percent of our lake-effect events are these narrow intense bands."
Previous research by Steenburgh showed a storm on Dec. 7, 1998 was essentially the result of the lake-effect snow alone. However, his latest study showed the lake-effect storm on Oct. 26-27, 2010 was caused by something completely different. The new study showed the lake-effect snows fell only because of the interaction between the Great Salt Lake and nearby mountains.