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Summertime influence of Asian pollution in the free troposphere over North America

Liang, Q. and Jaeglé, L. and Hudman, R. C. and Turquety, S. and Jacob, D. J. and Avery, M. A. and Browell, E. V. and Sachse, G. W. and Blake, D. R. and Brune, W. and Ren, X. and Cohen, R. C. and Dibb, J. E. and Fried, A. and Fuelberg, H. and Porter, M. and Heikes, B. G. and Huey, G. and Singh, H. B. and Wennberg, P. O. (2007) Summertime influence of Asian pollution in the free troposphere over North America. Journal of Geophysical Research D, 112 (D12). Art. No. D12S11. ISSN 0148-0227.

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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, O_3, HCN, PAN, C_2H_2, C_6H_6, methanol, and SO_4^(2–). The partitioning of NO_y species in the Asian plumes is dominated by PAN (∼600 pptv), with varying NO_x/HNO_3 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, C_3H_8, C_2H_6, C_6H_6) due to shorter summer lifetimes; higher levels of biogenic tracers (methanol and acetone) because of a more active biosphere; and higher levels of PAN, NO_x, HNO_3, and O_3 reflecting active photochemistry, possibly enhanced by efficient NO_y export and lightning. The high ΔO_3/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, O_3, PAN and NO_x.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Liang, Q.0000-0002-8430-0515
Jacob, D. J.0000-0002-6373-3100
Cohen, R. C.0000-0001-6617-7691
Dibb, J. E.0000-0003-3096-7709
Wennberg, P. O.0000-0002-6126-3854
Additional Information:© 2007 American Geophysical Union. Received 15 August 2006; revised 29 November 2006; accepted 11 January 2007; article first published online 11 May 2007. Work at the University of Washington was supported by funding from the National Science Foundation (ATM 0238530) and NASA. Please note: Wiley Blackwell is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
Funding AgencyGrant Number
Subject Keywords:intercontinental transport; Asia; ozone
Issue or Number:D12
Record Number:CaltechAUTHORS:20140702-110447278
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Official 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.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46636
Deposited By: Ruth Sustaita
Deposited On:02 Jul 2014 18:47
Last Modified:09 Mar 2020 13:18

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