Frequency of snowfall decreases in northwest, study shows

According to a new study from Portland State University, the average frequency of snowfall is expected to decrease by 2100 in the Pacific Northwest, and at a faster rate if greenhouse gas emissions are not reduced. not reduced.

Researchers at PSU's Climate Science Lab – Arielle Catalano, geography professor and climatologist – Paul Loikith and Christina Aragon – graduate student – examined the expected evolution of the number of days of snow in relation to the number of days in 157 SNOTEL stations in Oregon, Washington and Idaho. SNOTEL sites, or snowpack telemetry network, are often used to monitor water availability in mountainous areas and provide an observational baseline for defining snowfall. With the help of climate model projections, changes in the ratio of snow days to rain days are estimated relative to observations at these stations.

Catalano said calculating changes to locations used to monitor snowfall in the mountainous northwestern may provide information at scales relevant to those monitoring and managing water resources.

In the northwest, the snowpack is a natural reservoir that recharges groundwater and provides water during the drier summer months. Snowfall has an impact on water supply, which can affect agriculture, winter floods and recreational activities such as skiing and boating.

"These snow areas will begin to see an increasing proportion of rainfall fall in the form of rain," Catalano said. "This gives us an idea of ​​site-specific spatio-temporal changes, what is happening in this area and what we can expect to see on average in terms of snow versus rainy days over time. "

Among the results of the study, published in the journal Letters of geophysical research:

• By the end of the 21st century, more than 90% of SNOTEL stations in the North West will continue to receive snow, but many of these areas will experience more than half of the rainy days in the form of rain, which means more precipitation under rain rather than snow.
• Snowfall frequency decreases are greatest at low and medium elevation sites, such as the Cascades.

Catalano said global efforts to reduce greenhouse gas emissions can slow down the rate of decline. At virtually all stations, emissions would remain as before, resulting in a faster rate of decline throughout the second half of the 21st century, while lower emissions would result in lower rates.

"The overall frequency of snowfall would still be down, but at a slower pace," Catalano said.