An investigation of atmospheric rivers impacting heavy rainfall events in the North‐Central Mississippi River Valley

Abstract

During the latter part of the 20th century and into the 21st century, research has focused on evaluating how to more effectively utilize upper‐air soundings and satellite analysis of atmospheric water vapour transport pathways typically referred to as “atmospheric rivers” (ARs) in order to better forecast heavy rainfall events. Rainfall associated with ARs may include a significant portion of monthly and seasonal rainfall when they occur within the North‐Central Mississippi Valley Region. A comprehensive analysis of surface and upper‐air maps and upper‐air soundings and the associated vertical wind profiles is conducted to help build a relationship between the intensity and duration of heavy rainfall events during the period 2000–2015. The goal is to develop a proxy by which rainfall events can be predicted more accurately and work towards developing improved operational forecast protocols. In addition, a secondary goal is to evaluate possible connections between AR dynamics as highlighted using Hybrid Single‐Particle Lagrangian Integrated Trajectory (HYSPLIT) backwards trajectories, and the intensity as well as duration of heavy rainfall events. We find that while the synoptic‐scale pattern that produces ARs is similar to other AR studies, there are some differences in the synoptic‐scale environments consistent with the study of inter‐annual variability in this region. Also, while much of the moisture ingested by ARs comes from the Gulf and Caribbean, if moisture comes from the Atlantic region there is a potential for larger rainfall events. Finally, an analysis of upper‐air soundings shows some key differences between warm and cold season ARs, and possibly inter‐annual variations as well.