  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).
