Rain or snow? Citizen scientists help study Sierra storms (Opinion)

Monica Arienzo
Guest column

From record December snowfall to an exceptionally dry January, winter of 2021-22 has brought us a full range of weather extremes. Such variation in weather is common in our region. Even within a single storm we observe fluctuations in the phase of precipitation as it changes from snow to rain or vice versa. You may have experienced this when it is snowing at your house and then raining by the time you get to the ski resort.

These shifts from powdery snow to rain and slush are difficult to predict with computer models. A lot of that has to do with the fact that snow is common in our area, even when the air temperature is several degrees above freezing. The temperature at which snow transitions to rain depends, in part, on the humidity level.

This is a problem not only for those of us hitting the slopes or timing our trip over the pass, but also for the people managing our water resources, particularly when estimating the amount of water stored in mountain snowpacks.

How can we better predict if it will rain, snow, or be a mix of the two? Here is where you can help. Researchers can use citizen scientists’ observations of the phase of precipitation to better inform the computer models, which leads to better weather forecasting and management of precious water resources.

To that end, we launched a citizen science program in January 2020 called “Tahoe Rain or Snow.” Through this program, citizen scientists from the Lake Tahoe region submitted over 2,500 observations of snow, rain, or mixed precipitation. The data showed that precipitation transitions between rain and snow at temperatures closer to 39.5 degrees. This means that predictions made using the typical 32 degree threshold would under-predict snow.

Thanks to additional funding from NASA, our work continues, and volunteers from across the continent and the globe have added over 7,000 more observations to the database.

The project is now called “Mountain Rain or Snow,” and more observations from the Lake Tahoe region will advance our mission of better predicting phases of precipitation during winter storms. Anyone can submit observations of rain, snow, and mixed precipitation via your smartphone, laptop, desktop, tablet, or any other device with a web browser. Reports can be submitted from your backcountry adventures, while at the ski resort, or from the comfort of your own home.

Every observation is valuable. Additional reports from the Lake Tahoe region are especially needed to further refine the findings of our prior study. As you plan your next winter adventure, wouldn’t you like to know that it’s more likely to snow, even if the forecast calls for 38 degree weather?

One of the goals of the Tahoe Science Advisory Council is to improve our understanding of how Lake Tahoe is affected by climate change. We are hopeful that the information gathered from studies such as Mountain Rain or Snow will help better predict flooding and water resource availability today and into the future.

To sign up as a Mountain Rain or Snow citizen scientist text WINTER to 855-909-0798.

Monica Arienzo is part of the Desert Research Institute. Contributions to this column were made by the Mountain Rain or Snow Team: Keith Jennings (Lynker Technologies), Meghan Collins (DRI), Ben Hatchett (DRI), and Anne Nolin (University of Nevada, Reno), Josh Sturtevant (Lynker Technologies)

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