Event Title

Freezing Levels and Atmospheric Rivers over the California Feather River Watershed

Presenter Information

Julie Cunningham, Meteorology

Faculty Sponsor(s)

Jason Cordeira

Abstract

An atmospheric river (AR) is a long, narrow, and transient corridor of horizontal water vapor flux that primarily affects the west coasts of continents. The freezing level during an AR event can affect its impacts; a low (high) freezing level (Z0°C) will cause snow (rain). The Feather River Watershed (FRW) in northern California was examined to learn more about ARs, freezing levels, and related impacts near Lake Oroville, California’s second largest reservoir. The Rutz et al. (2014) AR catalog and NASA MERRA-2 reanalysis were used to analyze AR and freezing level characteristics, as well as precipitation and inflow data from the California Department of Water Resources. In the FRW’s cold season, 40% of the inflow at ORO is caused by the top 10% of periods with AR conditions, and 28% of the inflow is caused by the top 5% of periods. This demonstrates the need for accurate AR and freezing level forecasts to better prepare for reservoir levels and potential flooding hazards downstream. Top 10 Warm and Cold events from WY1981-2017 were identified by average freezing level per event and by precipitation greater than 1 inch in order to focus on extreme high and low events and their impacts.

Location

Hartman Union Building Courtroom

Start Date

5-2-2019 2:00 PM

End Date

5-2-2019 3:00 PM

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May 2nd, 2:00 PM May 2nd, 3:00 PM

Freezing Levels and Atmospheric Rivers over the California Feather River Watershed

Hartman Union Building Courtroom

An atmospheric river (AR) is a long, narrow, and transient corridor of horizontal water vapor flux that primarily affects the west coasts of continents. The freezing level during an AR event can affect its impacts; a low (high) freezing level (Z0°C) will cause snow (rain). The Feather River Watershed (FRW) in northern California was examined to learn more about ARs, freezing levels, and related impacts near Lake Oroville, California’s second largest reservoir. The Rutz et al. (2014) AR catalog and NASA MERRA-2 reanalysis were used to analyze AR and freezing level characteristics, as well as precipitation and inflow data from the California Department of Water Resources. In the FRW’s cold season, 40% of the inflow at ORO is caused by the top 10% of periods with AR conditions, and 28% of the inflow is caused by the top 5% of periods. This demonstrates the need for accurate AR and freezing level forecasts to better prepare for reservoir levels and potential flooding hazards downstream. Top 10 Warm and Cold events from WY1981-2017 were identified by average freezing level per event and by precipitation greater than 1 inch in order to focus on extreme high and low events and their impacts.