Central Valley’s air pollution might help boost Sierra snowfall
April 18, 2017
• Pollution particles help “seed” certain types of mountain clouds
• “It dramatically increases snow precipitation”
Some of the Central Valley air pollution that doesn’t get stuck in the lungs might end up helping increase Sierra snowfall, a new study suggests.
Water-ice clouds that slam into the mountains on the east side of the Valley have a dual response when injected with numerous tiny pollution particles, say scientists from Pacific Northwest National Laboratory and Colorado State University in a new paper published in Atmospheric Chemistry and Physics.
Mountain-side precipitation decreases at first but when the particles reach a certain amount, snowfall dramatically increases over the mountain.
The researchers say high concentrations of pollution particles wafting into the area lead to many more shallow clouds in the Central Valley and foothills, changing local circulation. Heat is given off when the cloud droplets form, strengthening movement of moisture to the windward slope.
"When the pollution particles fill the mountain-side mixed-phase clouds it dramatically increases snow precipitation, and this finding is different from previous modeling studies," says lead author Jiwen Fan who has studied the impact of pollution on precipitation for years.
"The mechanism leading to this cloud invigoration is our new finding," he says.
A better understanding of the processes that influence precipitation near mountains could help weather forecasters, skiers, farmers and water managers.