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October 26, 2021 – On Sunday morning, during the atmospheric river (AR) event in Northern California, scientists from the Center for Western Water Extremes (CW3E) at the Scripps Institute for Oceanography at UC San Diego and their partners at Yuba Water Agency launched weather balloons to gather data on the AR and its impacts on reservoirs.

Chad Hecht and Ava Cooper from the Center for Western Weather and Water Extremes at UC San Diego’s Scripps Institution of Oceanography. Photo courtesy YWA.

Similar to a 2019 launch, the balloons carried a radiosonde that captures temperature, humidity, wind speed and direction and atmospheric pressure data used by global weather models.

Data collected from these weather balloons directly contributed to understanding of the atmospheric river that made landfall in Northern California over the weekend.

According to John James, Yuba Water’s water operations manager and a trained atmospheric scientist, Sunday was a 200-year precipitation event that took place on the heels of a record-dry year in California, which underscores California’s extreme climate variability, something we expect to see increase in the future.

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The balloon, and more importantly its payload, can ascend as high as 15 miles into the atmosphere before the sensors fall back to earth, slowed by a parachute. The sensor data, transmitted in real time to the researchers, is part of a toolset used to create new forecasting model and procedures. 

Atmospheric river storms, which provide half of California’s annual precipitation, can cause major Yuba-Feather flood events. Forecast-Informed Reservoir Operations (FIRO) researches opportunities to improve reservoir operations and reduce flood risks by improving weather and runoff forecasts. The research is focused on both watersheds simultaneously, as Bullards and Oroville dams are operated in coordination to minimize downstream flood impacts.

Yuba Water Agency works closely with the CW3E, the California Department of Water Resources and others to improve forecasting and response to these storms to reduce flood risk for Yuba County and the region.

The weather balloons travel several hundred miles across the terrain. Most times the sensors can’t be recovered, but collecting data on both ascent and descent gives scientists a better picture of the conditions inside an atmospheric river.

This weekend’s AR added close to 39,000 acre feet (af) of water to New Bullards Bar Reservoir, bringing the reservoir storage to 411,546 af. The reservoir’s historical average for this date is 587,100 af of its total capacity of 966,000 af.