Evaluating Tornado Intensity and Interactions with Terrain via Remote Sensing of Treefall, Part 1: Overview

Existing studies have revealed the impact of terrain on tornado behavior. However, practical investigations involving empirical studies and real-world field assessments of such effects often encounter limitations, are restricted to small areas, or examine limited or simplistic terrain variations. This study examines two tornadoes that occurred on 10-11 December 2021. These tornadoes traversed the rough terrain and densely forested landscape of the Land Between the Lakes (LBL) National Recreation Area, located in both Kentucky and Tennessee. The observed damage suggests the occurrence of a violent tornado, where the terrain may have influenced the wind patterns and intensity. Through aerial imagery and ground truth plots, the team employed an approach involving uncrewed aerial systems (UAS) and the structure-from-motion (SfM) imaging technique. This data collection process spanned six days and resulted in almost 45,000 images capturing the paths of the two tornadoes within the LBL area (approximately 46 square kilometers). The very high resolution (approximately 2 cm) images enable post-event examination of terrain characteristics, fallen trees, and other intricate details that would be obscured in lower-resolution imagery. This presentation will focus on the methodology of gathering data through remote sensing, giving special emphasis to the UAS strategy, along with various approaches to evaluate tornado intensity based upon field observations and supplemental aerial and satellite imagery. This includes the analysis of point cloud vegetation height, spectral indices, brightness, texture, and supervised classification. The presentation includes a comparison of these varied approaches and an exploration of their inherent limitations.