Abstract
Temperature-related mortality is the leading cause of weather-related deaths in the United States. Herein, we explore the effect of air masses (AMs) – a relatively novel and holistic metric of human thermal comfort – on mortality across 61 different cities in the United States. Results show that AMs are significantly related to anomalous mortality in most US cities, and in most seasons. Of note, Humid-Warm (HW) air masses are associated with immediate increases in deaths in all seasons, however, mortality displacement only occurs outside of summer. The Warm and Dry-Warm AMs show slightly longer periods of increased mortality, albeit slightly less intensely as HW but with a similar lag structure by season. Two of the three cool AMs (Cool and Dry-Cool) each show a strong, but delayed mortality response in all seasons, with peak mortality 2 to 4 days after they occur, with the Dry-Cool AM having nearly a 15% risk of excess mortality. Meanwhile, the most seasonally consistent results are with transitional weather, whereby passing cold fronts are associated with a significant decrease in mortality 1 day after they occur, while warm fronts are associated with significant increases in mortality at that same lag time. Finally, artificial neural network modeling reveals that AM-mortality relationships gleaned from a combined meta-analysis can actually lead to more skillful modeling of these relationships than models trained on some individual cities, especially in the cities where such relationships might be masked due to low average daily mortality.