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Spatial Variation of Surface O3 Responses To Drought Over The Contiguous United States During Summertime: Role of Precursor Emissions and Ozone Chemistry

Abstract

Drought is an extreme weather and climate event that has been shown to cause the worsening of ozone (O3) air pollution. Using 15-year (2005–2019) surface O3 observations and weekly US Drought Monitor (USDM) indices, this study estimated that summertime US-mean surface O3 increased by 1.47 ppb per USDM level. It is revealed that O3 responses to drought display a spatial east-west variation: higher O3 enhancement in the Southeast (2.24 ppb/USDM), and no significant change or even a decrease in the west (e.g., −0.06 ppb/USDM in California). The diurnal changes of O3 with drought also show an opposite pattern between the Southeast and California. Formaldehyde (HCHO) and nitrogen dioxide (NO2) column, two satellite-based O3 precursors proxies, show an increasing rate of 0.41 × 1015 molec/cm2/USDM and 0.03 × 1015 molec/cm2/USDM in the Southeast, respectively, while these rates are not statistically significant in California. We explained this spatial discrepancy from the perspective of O3 chemistry by applying a zero-dimensional model at the sites with long-term observations in California and Georgia. Isoprene concentrations decreased by ∼37% under exceptional drought in California causing a reduction of O3 production (PO3) by ∼23.7% during daytime. On the contrary, isoprene increased by ∼41% in Georgia inducing a consequent increase of PO3 by ∼33.4% which accounts for more than half of the O3 enhancement. This study reveals the key role of biogenic isoprene on ozone chemistry under drought conditions.

Article / Publication Data
Active/Online
YES
Available Metadata
DOI ↗
Early Online Release
January 10, 2022
Fiscal Year
Peer Reviewed
YES
Publication Name
Jgr Atmospheres
Published On
January 16, 2022
Publisher Name
American Geophysical Union
Print Volume
127
Issue
1
Submitted On
July 26, 2021
URL ↗

Institutions

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Authors

Authors who have authored or contributed to this publication.

  • Wei Li - lead None
    Other
  • Jordan Schnell - sixth Gsl
    Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder
    NOAA/Global Systems Laboratory