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Tropospheric Ozone Assessment Report: Present-day ozone distribution and trends relevant to human health

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Author(s)

  • Zoë L. Fleming
  • Ruth M. Doherty
  • Erika von Schneidemesser
  • Christopher Malley
  • Owen R. Cooper
  • Joseph P. Pinto
  • Augustin Colette
  • Xiaobin Xu
  • David Simpson
  • Martin G. Schultz
  • Allen S. Lefohn
  • Samera Hamad
  • Raessa Moolla
  • Sverre Solberg
  • Zhaozhong Feng

Department/unit(s)

Publication details

JournalElementa: Science of the Anthropocene
DateAccepted/In press - 10 Dec 2017
DatePublished (current) - 5 Feb 2018
Issue number12
Volume6
Number of pages41
Original languageEnglish

Abstract

This study quantifies the present-day global and regional distributions (2010–2014) and trends (2000–2014) for five ozone metrics relevant for short-term and long-term human exposure. These metrics, calculated by the Tropospheric Ozone Assessment Report, are: 4th highest daily maximum 8-hour ozone (4MDA8); number of days with MDA8 > 70 ppb (NDGT70), SOMO35 (annual Sum of Ozone Means Over 35 ppb) and two seasonally averaged metrics (3MMDA1; AVGMDA8). These metrics were explored at ozone monitoring sites worldwide, which were classified as urban or non-urban based on population and nighttime lights data.Present-day distributions of 4MDA8 and NDGT70, determined predominantly by peak values, are similar with highest levels in western North America, southern Europe and East Asia. For the other three metrics, distributions are similar with North–South gradients more prominent across Europe and Japan. Between 2000 and 2014, significant negative trends in 4MDA8 and NDGT70 occur at most US and some European sites. In contrast, significant positive trends are found at many sites in South Korea and Hong Kong, with mixed trends across Japan. The other three metrics have similar, negative trends for many non-urban North American and some European and Japanese sites, and positive trends across much of East Asia. Globally, metrics at many sites exhibit non-significant trends. At 59% of all sites there is a common direction and significance in the trend across all five metrics, whilst 4MDA8 and NDGT70 have a common trend at ~80% of all sites. Sensitivity analysis shows AVGMDA8 trends differ with averaging period (warm season or annual). Trends are unchanged at many sites when a 1995–2014 period is used; although fewer sites exhibit non-significant trends. Over the longer period 1970–2014, most Japanese sites exhibit positive 4MDA8/SOMO35 trends. Insufficient data exist to characterize ozone trends for the rest of Asia and other world regions.

Bibliographical note

Copyright: © 2018 The Author(s). This is an open-access article distributed under the terms of the Creative Commons
Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original author and source are credited. See http://creativecommons.org/licenses/by/4.0/

    Research areas

  • ozone, trends, human health, global, metrics, present day

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