Attributing Seasonal Montane Snowfall Patterns to Atmospheric Rivers Using Different Detection Methods

Long, narrow moisture-rich low-level jets, known as atmospheric rivers (ARs), yield significant amounts of precipitation across the western United States. When ARs traverse mountain barriers, their strong vapor transport and abundant moisture promote orographic snowfall. This study examines the relationship between the AR detection method used and the diagnosed contribution of ARs to the seasonal cumulative snowfall (CS) across Sierra Nevada, USA. Utilizing a satellite integrated water vapor (IWV)-based approach and an atmospheric reanalysis integrated vapor transport (IVT)-based method, the corresponding AR-derived CS distributions were characterized during the winters of 1998-2015. Over the western (or windward) Sierra Nevada above 2100-2300 m, the IWV-based approach indicated that greater orographic enhancement of the seasonal CS was associated with ARs as opposed to non-AR storms. In contrast, greater enhancement was observed across all elevations with the IVT-based method. Moreover, the IWV-based approach diagnosed about half as many ARs as the IVT-based approach. This corresponds to an average 33% of the total range-wide CS annually attributed to ARs from the IWV-based detection method as opposed to 56% from the IVT-based detection method. Results indicate that the understanding of the AR-derived CS distribution and orographic enhancement depends on the detection method applied. Similar investigations that utilize a single IVT-based detection method and multiple atmospheric reanalyses are presented to provide insight into the sensitivity of the corresponding AR-derived CS distribution given different reanalyses. Findings highlight the importance of diagnosing specific meteorological events and understanding how detection methods and data sets have hydrological implications that may impact forecasts and hazard/risk assessments.