Semester of Graduation

Spring 2023


Master of Science (MS)


Geography and Anthropology

Document Type



Atmospheric river (AR) storms are an integral part of California’s hydrologic cycle, providing 30–50% of the state’s annual precipitation. However, “too much of a good thing” can swell

rivers beyond capacity leading to widespread flooding, erosion, and environmental damage. Northern California’s steep topography coupled with its seasonal Sierra Nevada snowpack puts this region at risk for floods and extreme weather hazards that can be triggered by strong ARs. Identifying AR contributions in the water cycle is crucial for informing water resource and emergency management decisions Stable isotope analysis provides a means to understand the movement of precipitation based on fractionation of isotopes in water molecules during phase changes. This study sought to identify an isotopic range and lapse rate for AR precipitation that allows us to distinguish them from other storm types impacting Northern California and understand their movement through the region’s complex terrain. Precipitation samples were collected at 26 locations along two transects of Northern California from October 2018 through April 2019 and analyzed using liquid water isotope laser spectroscopy. Storms sampled during this time interval were categorized as AR or non-AR storms using satellite imagery and integrated water vapor and vapor flux criteria. Statistical analyses revealed a significant difference in mean precipitation δ18O and δ2H between storm types. Assessment of isotopic lapse rates relative to elevation and distance from the coast found elevation explained more of the variability in precipitation isotope ratios per AR storms than distance with a 2‰/km decrease in δ18O with elevation and corresponding ~0.03‰ decrease in δ18O per km inland from the coast. By identifying a distinct isotopic range for AR precipitation, this information will be useful in hydrologic monitoring and water resource management applications as well as in paleoclimate reconstruction.



Committee Chair

DeLong, Kristine L.



Available for download on Saturday, April 04, 2026