A Climatology of Wet-Bulb Globe Temperature by Synoptic Weather Type with a Health Application

Heat is the leading cause of weather-related fatalities in the United States (U.S.), regularly exceeding other weather events including floods, tornadoes, and hurricanes. Several metrics have been developed to quantify heat due to its influence on society, agriculture, and energy consumption. One such metric is Wet-Bulb Globe Temperature (WBGT), which integrates temperature, humidity, wind speed, and solar radiation - four variables central to heat’s influence on the human body. Here, we develop a climatology of WBGT by synoptic weather type, as defined by the Spatial Synoptic Classification dataset, across the southeastern U.S. to quantify normal WBGT conditions and identify trends across different prevailing weather patterns. Additionally, we examine WBGT’s utility as a heat metric by statistically analyzing its association with morbidity and mortality across a twelve-year period in Louisiana using health data from the Louisiana Department of Health. We find that > 90% of negative health outcomes (e.g., emergency department visits, hospitalizations, and fatalities) occurred between April–October, a distinct difference in WBGT on days with no negative health outcomes, and WBGT exhibits a non-linear relationship with negative health outcomes. By developing a WBGT climatology and quantifying its association with negative health outcomes, we establish a baseline climatological understanding of WBGT and demonstrate its applicability to human health. As the climate continues to change, it is critically important to evaluate heat metrics and how they may affect society in a state like Louisiana, which has a highly vulnerable population. This work demonstrates how a WBGT climatology can be applied to better understand how people are currently affected by extreme heat and how they might be affected in the future.