Spatiotemporal Evolution of Heat Wave Severity and Coverage Across the United States

Abstract

Heat waves have pronounced impacts on human health, ecosystems, and society. Heat waves have become more frequent and intense globally and are likely to intensify further in a warming climate. Across the United States there is a warming trend in average surface temperatures, but concordant increase in heat wave severity appears absent. Limitations in heat waves studies may be responsible for limited detection of a heat wave warming signal. We track daily spatiotemporal evolution of heat waves using geometric concepts and clustering algorithms to investigate how heat manifests on the land surface. We develop a spatial metric combining heat wave frequency, magnitude, duration, and areal extent. We find mixed trends in some individual heat wave characteristics across the United States during 1981-2018. However, exploration of the spatiotemporal evolution of combined heat wave characteristics shows considerable increases during this period and indicates a substantial increase in heat wave hazard across the United States.Plain Language Summary Heat waves are detrimental to human health and the environment and are projected to intensify in the future. However, observed upward trends in heat wave severity have not previously been detected in some regions of the globe, including the United States. This study considers heat waves as spatiotemporal events allowing for detection of significant increases in severity and coverage across the United States. Our study outlines a novel approach that combines geometric concepts with a clustering algorithm to investigate how heat waves evolve. We track heat waves daily across the ground surface and capture the combination of frequency, magnitude, duration, and areal extent using a new index that provides a more complete picture of heat waves. Our results indicate significant increases in heat waves across the United States during the last four decades.

Interactive influence of ENSO and IOD on contiguous heatwaves in Australia

“…Contiguous heatwaves can be quantified by their total area, maximum area, median duration (Vogel et al 2020), and areal magnitude (Keellings and Moradkhani 2020). They are expressed as follows:…”

“…• Median duration: The median value of the duration of all grid cells associated with the contiguous heatwave. • Areal magnitude: Computed similarly as heat severity and convergence index defined by Keellings and Moradkhani (2020):…”

“…Lyon et al (2019) analysed these events across the United States and noticed increasing spatial extent under the RCP8.5 emission scenario. Keellings and Moradkhani (2020) examined the spatiotemporal evolution of contiguous heatwaves over different climate regions of the United States in the historical period , observing a substantial increase in the spatial coverage of contiguous heatwaves. Vogel et al (2020) investigated projections of large contiguous heatwaves globally by considering neighbouring countries as contiguous regions and found that they will substantially increase under the RCP8.5 emissions scenario.…”

Anthropogenic Warming and Population Growth May Double US Heat Stress by the Late 21st Century

“…Extreme heat events in the CONUS in recent decades have trended toward earlier springtime occurrence and increased severity, frequency, and areal extent (Smith et al., 2013). These trends appear connected to anthropogenic warming (Keellings & Moradkhani, 2020; Knutson & Ploshay, 2016; Wang et al., 2020). Critically, increasing global temperatures bring with them increasing moisture, leading to projections of heat stress that are both larger and higher‐confidence than those for temperature alone (Fischer & Knutti, 2013; Raymond et al., 2020).…”

Spatiotemporal Variation Analysis of the Fine-Scale Heat Wave Risk along the Jakarta-Bandung High-Speed Railway in Indonesia

“…A review of the current literature on HWR assessment worldwide reveals the following problems: (1) In terms of the time scale, most of the studies on HWR changes at long time scales are based on meteorological station data, and only indicators of the heat wave intensity, frequency and duration are chosen [17][18][19][20][21], or indicators such as the effective cumulative temperature calculated considering meteorological station temperature data [22] to study heat waves in a particular region over decades. However, studies based on meteorological station data consider only one station to represent the temperature of the whole city, or when the study area is large, the variability in heat waves is mostly studied via interpolation of station-measured temperatures [20,21,23].…”