Land surface heterogeneity and tornado occurrence: an analysis of Tornado Alley and Dixie Alley

Tornadoes rank among the most destructive hazards to human life and property. In the United States, two regions known as Tornado Alley and Dixie Alley are particularly prone to tornadoes, but determining exactly where tornadoes will occur remains difficult. Examining the relationship between land surface heterogeneity (i.e. variations in topography, vegetation, and land cover) and tornado occurrence can provide insight into the spatial distribution of these storms. The objective of this study is to uncover the relationships between severe storm occurrence and land surface heterogeneity variables to determine (1) whether certain land heterogeneity variables exhibit a significant relationship with tornado occurrence, and (2) whether those relationships vary by region and storm strength. We delineate the spatial extent of Tornado Alley and Dixie Alley based on clusters of tornadic activity. We then use logistic regression to investigate how land heterogeneity factors are related to tornado formation of weakly and significantly tornadic storms. Using these relationships uncovered, we map tornado probability across the two regions. Regression results show that several land surface heterogeneity variables have a statistically significant relationship with tornado occurrence, but these relationships vary with region and storm severity, supporting the need for more local studies.