Tornado casualty rates in the United States

Authors: James Elsner*, Florida State University, Tyler Fricker, Florida State University
Topics: Hazards and Vulnerability, Climatology and Meteorology
Keywords: hazards, tornado, vulnerability
Session Type: Paper
Day: 4/14/2018
Start / End Time: 2:00 PM / 3:40 PM
Room: Napoleon B3, Sheraton 3rd Floor
Presentation File: No File Uploaded

Recent research showed the importance of combining tornado strength and the number of people exposed in statistically estimating the risk of death or injury. The interaction between the two factors was fixed under the assumption of constant vulnerability. Here we relax this assumption by adding a product term to the model and find that the percentage increase in casualty rates (per casualty-producing tornado) with increasing energy dissipation {\it increases} with population density. The results implies a gradient in tornado vulnerability across population density. Fitting the model to casualty counts grouped by state reveals that the vulnerability gradient is steepest across Arkansas, Tennessee, and Missouri. Controlling for energy dissipation, casualty rates are substantially higher in more densely populated areas of these states in the Mid South than in similarly populated areas elsewhere. Casualty rates are not significantly different at night through a broad range of energy dissipation values and population exposures. Thus the higher relative incidence of nocturnal tornadoes across the South including Arkansas, Tennessee, and Missouri does not explain the gradient in vulnerability. Also, casualty rates are {\it higher} during the weekend than during the week.

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