Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Co-occurrence of extremes in surface ozone, particulate matter, and temperature over eastern North America

TitleCo-occurrence of extremes in surface ozone, particulate matter, and temperature over eastern North America
Publication TypeJournal Article
Year of Publication2017
AuthorsSchnell, Jordan L., and Prather Michael J.
JournalPNAS
Volume114
Number11
Pages2854-2859
Abstract / Summary

Heat waves and air pollution episodes pose a serious threat to human health and may worsen under future climate change. In this paper, we use 15 years (1999–2013) of commensurately gridded (1° x 1°) surface observations of extended summer (April–September) surface ozone (O3), fine particulate matter (PM2.5), and maximum temperature (TX) over the eastern United States and Canada to construct a climatology of the coincidence, overlap, and lag in space and time of their extremes. Extremes of each quantity are defined climatologically at each grid cell as the 50 d with the highest values in three 5-y windows (∼95th percentile). Any two extremes occur on the same day in the same grid cell more than 50% of the time in the northeastern United States, but on a domain average, co-occurrence is approximately 30%. Although not exactly co-occurring, many of these extremes show connectedness with consistent offsets in space and in time, which often defy traditional mechanistic explanations. All three extremes occur primarily in large-scale, multiday, spatially connected episodes with scales of >1,000 km and clearly coincide with large-scale meteorological features. The largest, longest-lived episodes have the highest incidence of co-occurrence and contain extreme values well above their local 95th percentile threshold, by +7 ppb for O3, +6 µg m−3 for PM2.5, and +1.7 °C for TX. Our results demonstrate the need to evaluate these extremes as synergistic costressors to accurately quantify their impacts on human health.

URLhttp://dx.doi.org/10.1073/pnas.1614453114
DOI10.1073/pnas.1614453114
Journal: PNAS
Year of Publication: 2017
Volume: 114
Number: 11
Pages: 2854-2859
Publication Date: 03/2017

Heat waves and air pollution episodes pose a serious threat to human health and may worsen under future climate change. In this paper, we use 15 years (1999–2013) of commensurately gridded (1° x 1°) surface observations of extended summer (April–September) surface ozone (O3), fine particulate matter (PM2.5), and maximum temperature (TX) over the eastern United States and Canada to construct a climatology of the coincidence, overlap, and lag in space and time of their extremes. Extremes of each quantity are defined climatologically at each grid cell as the 50 d with the highest values in three 5-y windows (∼95th percentile). Any two extremes occur on the same day in the same grid cell more than 50% of the time in the northeastern United States, but on a domain average, co-occurrence is approximately 30%. Although not exactly co-occurring, many of these extremes show connectedness with consistent offsets in space and in time, which often defy traditional mechanistic explanations. All three extremes occur primarily in large-scale, multiday, spatially connected episodes with scales of >1,000 km and clearly coincide with large-scale meteorological features. The largest, longest-lived episodes have the highest incidence of co-occurrence and contain extreme values well above their local 95th percentile threshold, by +7 ppb for O3, +6 µg m−3 for PM2.5, and +1.7 °C for TX. Our results demonstrate the need to evaluate these extremes as synergistic costressors to accurately quantify their impacts on human health.

DOI: 10.1073/pnas.1614453114
Citation:
Schnell, JL, and MJ Prather.  2017.  "Co-occurrence of extremes in surface ozone, particulate matter, and temperature over eastern North America."  PNAS 114(11): 2854-2859.  https://doi.org/10.1073/pnas.1614453114.