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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 112,
D12S11,
doi:10.1029/2006JD007919,
2007
Summertime influence of Asian pollution in the free troposphere over North America
Q. Liang
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
L. Jaeglé
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
R. C. Hudman
Division of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, USA
S. Turquety
Division of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, USA
D. J. Jacob
Division of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, USA
M. A. Avery
NASA Langley Research Center, Hampton, Virginia, USA
E. V. Browell
NASA Langley Research Center, Hampton, Virginia, USA
G. W. Sachse
NASA Langley Research Center, Hampton, Virginia, USA
D. R. Blake
Department of Chemistry, University of California, Irvine, California, USA
W. Brune
Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania, USA
X. Ren
Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania, USA
R. C. Cohen
Department of Chemistry, University of California, Berkeley, California, USA
J. E. Dibb
Climate Change Research Center, University of New Hampshire, Durham, New Hampshire, USA
A. Fried
Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA
H. Fuelberg
Department of Meteorology, Florida State University, Tallahassee, Florida, USA
M. Porter
Department of Meteorology, Florida State University, Tallahassee, Florida, USA
B. G. Heikes
Department of Oceanography, University of Rhode Island, Narragansett, Rhode Island, USA
G. Huey
School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
H. B. Singh
NASA Ames Research Center, Moffett Field, California, USA
P. O. Wennberg
California Institute of Technology, Pasadena, California, USA
Abstract
We analyze aircraft observations obtained during INTEX-A (1 July to 14 August 2004) to examine the summertime influence of
Asian pollution in the free troposphere over North America. By applying correlation analysis and principal component analysis
(PCA) to the observations between 6 and 12 km, we find dominant influences from recent convection and lightning (13% of observations),
Asia (7%), the lower stratosphere (7%), and boreal forest fires (2%), with the remaining 71% assigned to background. Asian
air masses are marked by high levels of CO, O3, HCN, PAN, C2H2, C6H6, methanol, and SO4 2–. The partitioning of NOy species in the Asian plumes is dominated by PAN (∼600 pptv), with varying NOx/HNO3 ratios in individual plumes, consistent with individual transit times of 3–9 days. Export of Asian pollution occurred in
warm conveyor belts of midlatitude cyclones, deep convection, and in typhoons. Compared to Asian outflow measurements during
spring, INTEX-A observations display lower levels of anthropogenic pollutants (CO, C3H8, C2H6, C6H6) due to shorter summer lifetimes; higher levels of biogenic tracers (methanol and acetone) because of a more active biosphere;
and higher levels of PAN, NOx, HNO3, and O3 reflecting active photochemistry, possibly enhanced by efficient NOy export and lightning. The high ΔO3/ΔCO ratio (0.76 mol/mol) in Asian plumes during INTEX-A is due to strong photochemical production and, in some cases, mixing
with stratospheric air along isentropic surfaces. The GEOS-Chem global model captures the timing and location of the Asian
plumes. However, it significantly underestimates the magnitude of observed enhancements in CO, O3, PAN and NOx.
Received 15
August
2006;
accepted 11
January
2007;
published 11
May
2007.
Keywords: intercontinental transport;
Asia;
ozone.
Index Terms: 0368 Atmospheric Composition and Structure: Troposphere: constituent transport and chemistry; 0345 Atmospheric Composition and Structure: Pollution: urban and regional (0305, 0478, 4251); 0365 Atmospheric Composition and Structure: Troposphere: composition and chemistry.
Read Full Article (file size: 14569783 bytes) Cited by
Citation: Liang, Q., et al.
(2007),
Summertime influence of Asian pollution in the free troposphere over North America,
J. Geophys. Res.,
112,
D12S11,
doi:10.1029/2006JD007919.
Copyright 2007 by the American Geophysical Union.
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