A Study of Two Impactful Heavy Rainfall Events in the Southern Appalachian Mountains during Early 2020, Part II; Regional Overview, Rainfall Evolution, and Satellite QPE Utility

Douglas Miller,Shuyan Liu,Shaorong Wu,Malarvizhi Arulraj,Bob Kuligowski,Veljko Petkovic,Pingping Xie,Christopher Grassotti,Ralph Ferraro

doi:10.3390/rs13132500

Abstract

Two heavy rainfall events occurring in early 2020 brought flooding, flash flooding, strong winds, and tornadoes to the southern Appalachian Mountains. Part I of the study examined large-scale atmospheric contributions to the atmospheric river-influenced events and subsequent societal impacts. Contrary to expectations based on previous work in this region, the event having a lower event accumulation and shorter duration resulted in a greater number of triggered landslides and prolonged downstream flooding outside of the mountains. One purpose of this study (Part II) is to examine the local atmospheric conditions contributing to the rather unusual surface response to the shorter duration heavy rainfall event of 12–13 April 2020. A second purpose of this study is to investigate the utility of several spaced-based QPE and vertical atmospheric profile methods in illuminating some of the atmospheric conditions unique to the April event. The embedded mesoscale convective elements in the warm sector of the April event were larger and of longer duration than of the other event in February 2020, leading to sustained periods of convective rain rates. The environment of the April event was convectively unstable, and the resulting available potential energy was sustained by relatively dry airstreams at the 700 hPa level, continuously overriding the moist air stream at low levels attributed to an atmospheric river.

Highlights

Part I of this study focused on the large-scale weather and surface features contributing to two heavy rainfall events in early 2020 triggering numerous landslides in the mountains of western North Carolina [1]
Geologic factors of slope and lithology, the variable factors of runoff, percolation and storage of moisture and their interaction within the deeper soil layers determine if a region is predisposed to landslides when a storm of sufficient precipitation intensity can serve as the trigger
Selected periods during the trigger phases of each event corresponded to the time when the associated atmospheric river (AR) of moisture was centered on the southern Appalachian Mountains; 1200 UTC

Summary

Introduction

Part I of this study focused on the large-scale weather and surface features contributing to two heavy rainfall events in early 2020 triggering numerous landslides in the mountains of western North Carolina [1]. Geologic factors of slope and lithology, the variable factors of runoff, percolation and storage of moisture and their interaction within the deeper soil layers determine if a region is predisposed to landslides when a storm of sufficient precipitation intensity can serve as the trigger. The latter factors involve change at relatively long time scales relative to the atmospheric factors due to the limited movement of water through porous soil. The concept of watershed “memory” in which the latter factors were linked to precipitation events in the recent and distant past was studied in the Coweeta River sub-Basin (CRB)

Methods

Results

Discussion

Conclusion