May 22 - July 28
Compound Heat Wave and PM2.5 Pollution Episodes in U.S. Cities
Sarah Henry and Chenghao Wang
What is already known:
- Heat waves are becoming more frequent, more intense, and longer lasting in the 21st century
- The Urban Heat Island effect can amplify heat waves and their impacts within the urban environment
- Wildfire events are increasing in the United States and Canada and can cause episodes of increased air pollution, specifically PM2.5
- An urban environment’s background climate affects ways these events impact it
What this study adds:
- An analysis of heat waves, PM2.5 air pollution episodes, and compound heat wave and air pollution episodes for 481 urban areas and their surrounding rural areas in the contiguous United States
- Heat waves primarily impact the West and Southwest regions
- Air pollution episodes primarily impact the Ohio Valley, Southeast, and Northeast regions, but are the most intense in the Northern Rockies and Plains and Upper Midwest regions
- Compound heat wave and air pollution episodes primarily impact the Ohio Valley, Southeast, and Northeast regions in frequency, intensity in pollution, and duration, but are the most intense in heat in the West and Southwest regions
- Heat waves and compound heat wave and air pollution episodes have a greater impact on the majority of urban areas compared to rural areas, while air pollution episodes have a greater impact on only some of the urban areas compared to rural areas
Abstract:
This study analyzes heat waves (HWs), air pollution (AP) episodes, and compound HW and AP events (CE) in the urban environment and provides a comparison between events in urban areas (UAs) and rural areas (RAs). A 1-km gridded daily minimum temperature dataset and a 1-km gridded daily PM2.5 concentration dataset were used along with geospatial data to characterize events by their frequency, intensity in heat, intensity in pollution, and duration. The greatest differences between UAs and RAs in frequency, heat intensity, pollution intensity, and duration for all events were seen in the West and Southwest regions. For both UAs and RAs, it was found that HWs were the most frequent, intense, and longest lasting in the West and Southwest regions, AP episodes were the most frequent and longest lasting in the Northeast, Ohio Valley, and Southeast regions, and AP episodes were the most intense in the Northern Rockies and Plains and Upper Midwest regions. It was concluded that HWs (AP episodes) had a greater impact on CEs than AP episodes (HWs) in regions with more prominent HWs (AP episodes).