Changes in the photochemical environment of the temperate North Pacific troposphere in response to increased Asian emissions

Authors

D. D. Parrish, National Oceanic and Atmospheric Administration
E. J. Dunlea, National Oceanic and Atmospheric Administration
E. L. Atlas, The Earth and Sun Systems LaboratoryFollow
S. Schauffler, The Earth and Sun Systems Laboratory
Stephen G. Donnelly Ph.D., The Earth and Sun Systems LaboratoryFollow
V. Stroud, The Earth and Sun Systems Laboratory
A. H. Goldstein, Department of Environmental Science, Policy, and Management
D. B. Millet, Department of Environmental Science, Policy, and Management
M. McKay, Department of Environmental Science, Policy, and Management
D. A. Jaffe, University of Washington-Bothell
H. U. Price, University of Washington-Bothell
P. G. Hess, The Earth and Sun Systems Laboratory
F. Flocke, The Earth and Sun Systems LaboratoryFollow
J. M. Roberts, National Oceanic and Atmospheric AdministrationFollow

Abstract

Measurements during the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) field study characterized the springtime, eastern Pacific ozone distribution at two ground sites, from the National Oceanic and Atmospheric Administration WP-3D aircraft, and from a light aircraft operated by the University of Washington. D. Jaffe and colleagues compared the 2002 ozone distribution with measurements made in the region over the two previous decades and show that average ozone levels over the eastern midlatitude Pacific have systematically increased by ∼10 ppbv in the last two decades. Here we provide substantial evidence that a marked change in the photochemical environment in the springtime troposphere of the North Pacific is responsible for this increased O3. This change is evidenced in the eastern North Pacific ITCT 2K2 study region by (1) larger increases in the minimum observed ozone levels compared to more modest increases in the maximum levels, (2) increased peroxyacetyl nitrate (PAN) levels that parallel trends in NOx, emissions, and (3) decreased efficiency of photochemical O3 destruction, i.e., less negative O3 photochemical tendency (or net rate of O3 photochemical production; P(O3)). This change photochemical environment is hypothesized to be due to anthropogenic emissions from Asia, which are believed to have substantially increased over the two decades preceding the study. We propose that their influence has changed the springtime Pacific tropospheric photochemistry from predominately ozone destroying to more nearly ozone producing. However, chemical transport model calculations indicate the possible influence of a confounding factor; unusual transport of tropical air to the western North Pacific during one early field study may have played a role in this apparent change in the photochemistry. Copyright 2004 by the American Geophysical Union.

Document Type

Article

Source Publication

Journal of Geophysical Research D: Atmospheres

Version

Published version

DOI

10.1029/2004JD004978

Publication Date

12-16-2004

Volume

109

Issue

23

First Page

1

Last Page

16

Rights

© American Geophysical Union

Comments

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Recommended Citation

Parrish, D. D., et al. (2004), Changes in the photochemical environment of the temperate North Pacific troposphere in response to increased Asian emissions, J. Geophys. Res., 109, D23S18, doi:10.1029/2004JD004978.