The Influence of Atmospheric Rivers on Extreme Precipitation Events Observed in the Southern Appalachians

Lukas Stewart


The central purpose of this project is to improve the understanding of Atmospheric Rivers (ARs), narrow lower-tropospheric air streams having high amounts of integrated water vapor, and the meteorological factors that produce flooding by ARs through investigating the influence of extreme precipitation in the southern Appalachian Mountains. Recently, much research has been conducted in order to find the impact of ARs on precipitation events in the United States. AR climatology suggests that precipitation of the Appalachian Mountains is minimally influenced by ARs, compared to regions immediately upstream and downstream of the mountains.1 An outcome of the proposed study will be to test if this result is robust, supported by true atmospheric processes, or if Lavers and Villarini’s AR climatology is an artifact of the difficulty in estimating precipitation in remote locations of the mountains. If ARs indeed prove to be an important contributor to the production of heavy precipitation events in the southern Appalachian Mountains, they can provide a good warning flag to the operational forecaster as their spatial and temporal evolution occur on scales large enough that they are detectable and predictable via current technological capabilities. The research methodology includes: (1) examining a five-year climatology of satellite total precipitable water (TPW) observations, mid- and high- elevation rain gauge network observations, USGS river and stream gauge observations, and gridded atmospheric data to determine the frequency of ARs impacting the southern Appalachians and the intensity of precipitation and severity of flooding that occurs during the interaction with the mountains, (2) collecting and archiving AR-influenced case studies with significant societal impacts in order to assemble a storm atlas, and (3) diagnosing the associated synoptic and/or mesoscale conditions favorable for maximizing the production of intense rainfall.

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