Traditional hydrologic models may misidentify snow as rain, new citizen science data shows

February 22, 2021

Reno, Nev. (Feb. 22, 2021)- Normally, we think of the freezing point of water as 32°F - but in the world of weather forecasting and hydrologic prediction, that isn't always the case. In the Lake Tahoe region of the Sierra Nevada, the shift from snow to rain during winter storms may actually occur at temperatures closer to 39.5°F, according to new research from the Desert Research Institute (DRI), Lynker Technologies, and citizen scientists from the Tahoe Rain or Snow project

The new paper, which published this month in Frontiers in Earth Science, used data collected by 200 volunteer weather spotters to identify the temperature cutoff between rain and snow in winter storms that occurred during the 2020 season. Their results have implications for the accuracy of water resources management, weather forecasting, and more.

"Scientists use a temperature threshold to determine where and when a storm will transition from rain to snow, but if that threshold is off, it can affect our predictions of flooding, snow accumulation, and even avalanche formation," said Keith Jennings, Ph.D., Water Resources Scientist at Lynker Technologies and one of the lead authors on the study.

Previous studies have found that thresholds used are particularly problematic in the Sierra Nevada, where a significant proportion of winter precipitation falls near 32°F. When the temperature is near freezing, weather forecasts and hydrologic models have difficulty correctly predicting whether it will be raining or snowing.

Tahoe Rain or Snow was launched in 2019 to take on the challenge of enhancing the prediction of snow accumulation and rainfall that may lead to flooding by making real-time observations of winter weather. The team is comprised of two scientists, one education specialist, and about 200 volunteer weather spotters from the Lake Tahoe and western slope regions of the Sierra Nevada and Truckee Meadows.

"Tahoe Rain or Snow harnesses the power of hundreds of local volunteers. The real-time observations that they share with scientists add an incredible amount of value to the study of hydrology and clarify crucial gaps left by weather models," said Meghan Collins, MS, Education Program Manager for DRI and another lead author on the paper.

In 2020, these citizen scientists submitted over 1,000 timestamped, geotagged observations of precipitation phase through the Citizen Science Tahoe mobile phone app. Ground-based observations submitted by the Tahoe Rain or Snow team in 2020 showed that a much warmer temperature threshold of 39.5°F for splitting precipitation into rain and snow may be more accurate for our mountain region. In contrast, a 32°F rain-snow temperature threshold would have vastly overpredicted rainfall, leading to pronounced underestimates of snow accumulation. Such model errors can lead to issues in water resources management, travel planning, and avalanche risk prediction.

"Tahoe Rain or Snow citizen scientists across our region open a door to improve our understanding of winter storms", said Monica Arienzo, Ph.D., Assistant Research Professor of Hydrology at DRI and another lead author on the paper. "Growing our team of volunteer scientists is important given that climate change is causing the proportion of precipitation falling as snow to decrease, and they help enhance the predictions of precipitation that we rely on in the Sierra Nevada and Truckee Meadows."

Tahoe Rain or Snow is continuing in 2021. To join, text WINTER to 877-909-0798. You will find out how to download the Citizen Science Tahoe app and receive alerts as to good times to send weather observations. Tahoe Rain or Snow particularly needs observations from sparsely populated, remote, or backcountry areas of the Sierra Nevada.
-end-
More information:

For more information on the Tahoe Rain or Snow project, please visit: https://www.dri.edu/project/tahoe-rain-or-snow/

Desert Research Institute

Related Precipitation Articles from Brightsurf:

Convection-permitting modelling improves simulated precipitation over the Tibetan Plateau
A China-UK research team explains the possible reasons for excessive precipitation over the TP in the mesoscale convection-parameterized models.

Spread of monsoon circulation changes explains uncertainty in global land monsoon precipitation projection
A new study emphasizes the importance of reliable prediction of circulation changes, to ensure that future projections of global land monsoon are suitable for use by policy makers.

GMMIP simulations on global monsoon interannual variability show higher skill than historical simulations
GMMIP simulations on global monsoon interannual variability show higher skill than historical simulations.

The spatial consistency of summer rainfall variability between the Mongolian Plateau and North China
The regional differences and similarities of precipitation variability are hotspots in climate change research.

Scientists find key factors impacting sideswiping tropical cyclone precipitation
Scientists find that the distribution of sideswiping tropical cyclones precipitation(STP) includes extreme STP events that appear not only over the island and coastal areas, but also over inland areas

Rainy season tends to begin earlier in Northern Central Asia
The researchers found robust increase of annual mean precipitation at the end of the 21st century under all modelling scenarios over northern central Asia.

Using cloud-precipitation relationship to estimate cloud water path of mature tropical cyclones
Scientists find the cloud water path of mature tropical cyclones can be estimated by a notable sigmoid function of near-surface rain rate.

Precipitation will be essential for plants to counteract global warming
A new Columbia Engineering study shows that increased water stress--higher frequency of drought due to higher temperatures, is going to constrain the phenological cycle: in effect, by shutting down photosynthesis, it will generate a lower carbon uptake at the end of the season, thus contributing to increased global warming.

Fall precipitation predicts abundance of curly top disease and guides weed management
Transmitted by an insect known as the beet leafhopper, curly top disease is a viral disease affecting many crops, including melons, peppers, sugar beets, and tomatoes.

Study confirms climate change impacted Hurricane Florence's precipitation and size
A new modeling framework showed that Hurricane Florence produced more extreme rainfall and was spatially larger due to human-induced climate change.

Read More: Precipitation News and Precipitation Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.