HR: 09:00h
AN: A51E-04    [Abstracts]
TI: Can we Detect an Influence over North America From Increasing Asian NOx Emissions?
AU: * Jaffe, D A
EM: djaffe@u.washington.edu
AF: University of Washington, Bothell, 18115 Campus Way NE, Bothell, WA 98011, United States
AU: Thornton, J
EM: thornton@atmos.washington.edu
AF: University of Washington, Atmospheric Sciences, 408 ATG Building, Seattle, WA 98195, United States
AU: Wolfe, G
EM: gwolfe@u.washington.edu
AF: University of Washington, Atmospheric Sciences, 408 ATG Building, Seattle, WA 98195, United States
AU: Reidmiller, D
EM: dreidm@atmos.washington.edu
AF: University of Washington, Atmospheric Sciences, 408 ATG Building, Seattle, WA 98195, United States
AU: Fischer, E V
EM: efischer@atmos.washington.edu
AF: University of Washington, Atmospheric Sciences, 408 ATG Building, Seattle, WA 98195, United States
AU: Jacob, D J
EM: djacob@fas.harvard.edu
AF: Harvard University, Engineering & Applied Sciences, 29 Oxford Street, Cambridge, MA 02138, United States
AU: Zhang, L
EM: linzhang@fas.harvard.edu
AF: Harvard University, Engineering & Applied Sciences, 29 Oxford Street, Cambridge, MA 02138, United States
AU: Cohen, R
EM: cohen@cchem.berkeley.edu
AF: University of California, Berkeley, College of Chemistry, 420 Latimer Hall, Berkeley, CA 94720, United States
AU: Singh, H
EM: hsingh@mail.arc.nasa.gov
AF: NASA Ames Research Center, Moffett Field, Moffett Field, CA 94035, United States
AU: Weinheimer, A
EM: wein@ucar.edu
AF: NCAR, P. O. Box 3000, Boulder, CO 80307-3000, United States
AU: Flocke, F
EM: ffl@ucar.edu
AF: NCAR, P. O. Box 3000, Boulder, CO 80307-3000, United States
AB: Several studies have reported a rapid increase in Asian NOx emissions. This knowledge, combined with our observations of long-range transport and global chemical transport models, suggests that we may soon be able to identify an influence on atmospheric composition over the Eastern Pacific and North American regions. Using the GEOS-CHEM model, we find that the Asian contribution to PAN in the free troposphere over the Eastern Pacific is approximately 50%. To estimate the magnitude of change in the Eastern Pacific troposphere we might expect from the recent Asian emission changes, we have conducted two simulations, one with standard emissions inventory and one with doubled emissions of NOx and NMHC from East Asia. Based on published data, a doubling of NOx emissions would be approximately correct for the period of 1999-2007. This simulation yields small changes in NOx and O3 (20% and 7%, respectively) but larger changes in mean PAN mixing ratios (43%) in the Eastern Pacific. Thus it appears that PAN is the most sensitive indicator of Asian NOx emissions in the Pacific troposphere. However, the simulation is very sensitive to NMHC emissions, which are not known with high accuracy. We can evaluate these changes with aircraft, surface and mountain top observations of PAN, NOx and O3 over the Eastern Pacific/western North America between 1999 and 2007. Measurements of PAN, NO and O3 were made by aircraft over the Eastern Pacific in 1999 during the PHOBEA campaign (Kotchenruther et al., 2001). Aircraft observations were made in the same region in 2006 during the INTEX campaign. In addition, free tropospheric observations at the Mt. Bachelor Observatory (MBO) have been carried out since 2004. O3 in the Eastern Pacific shows strong interannual variability which makes it difficult to tease out smaller long-term changes from the aircraft data. On the other hand, long-term observations of surface O3 in western North America have shown a significant increase at numerous rural sites during this time period, but multiple factors may be responsible for these changes. For NOx, comparing aircraft observations in the Eastern Pacific between 1999 and 2006 and considering the uncertainty in the observations, we find no evidence for a significant change. For PAN, comparing aircraft observations made in 1999 and 2006, and MBO free tropospheric observations in 2006 we see evidence for a significant enhancement in PAN over this time frame. The aircraft observations yield an enhancement of 22% in the free tropospheric mixing ratios, whereas the MBO free tropospheric observations suggest a larger enhancement (~100%). The observations are consistent with an emerging trend in PAN in the Eastern Pacific region, although further observations are needed to confirm.
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting