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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, D23S11, doi:10.1029/2004JD004513, 2004

Multiscale simulations of tropospheric chemistry in the eastern Pacific and on the U.S. West Coast during spring 2002

Youhua Tang

Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA


Gregory R. Carmichael

Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA


Larry W. Horowitz

Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, New Jersey, USA


Itsushi Uno

Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan


Jung-Hun Woo

Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA


David G. Streets

Decision and Information Sciences Division, Argonne National Laboratory, Argonne, Illinois, USA


Donald Dabdub

Department of Mechanical and Aerospace Engineering, University of California, Irvine, California, USA


Gakuji Kurata

Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi, Japan


Adrian Sandu

Department of Computer Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA


James Allan

Department of Physics, University of Manchester Institute of Science and Technology, Manchester, UK


Elliot Atlas

National Center for Atmospheric Research, Boulder, Colorado, USA


Franck Flocke

National Center for Atmospheric Research, Boulder, Colorado, USA


Lewis Gregory Huey

School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA


Roger O. Jakoubek

Aeronomy Laboratory, NOAA, Boulder, Colorado, USA


Dylan B. Millet

Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA


Patricia K. Quinn

Pacific Marine Environmental Laboratory, NOAA, Seattle, Washington, USA


James M. Roberts

Aeronomy Laboratory, NOAA, Boulder, Colorado, USA


Douglas R. Worsnop

Aerodyne Research Inc., Billerica, Massachusetts, USA


Allen Goldstein

Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA


Stephen Donnelly

National Center for Atmospheric Research, Boulder, Colorado, USA


Sue Schauffler

National Center for Atmospheric Research, Boulder, Colorado, USA


Verity Stroud

National Center for Atmospheric Research, Boulder, Colorado, USA


Kristen Johnson

National Center for Atmospheric Research, Boulder, Colorado, USA


Melody A. Avery

NASA Langley Research Center, Hampton, Virginia, USA


Hanwant B. Singh

NASA Ames Research Center, Moffett Field, California, USA


Eric C. Apel

National Center for Atmospheric Research, Boulder, Colorado, USA


Abstract

Regional modeling analysis for the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) experiment over the eastern Pacific and U.S. West Coast is performed using a multiscale modeling system, including the regional tracer model Chemical Weather Forecasting System (CFORS), the Sulfur Transport and Emissions Model 2003 (STEM-2K3) regional chemical transport model, and an off-line coupling with the Model of Ozone and Related Chemical Tracers (MOZART) global chemical transport model. CO regional tracers calculated online in the CFORS model are used to identify aircraft measurement periods with Asian influences. Asian-influenced air masses measured by the National Oceanic and Atmospheric Administration (NOAA) WP-3 aircraft in this experiment are found to have lower ΔAcetone/ΔCO, ΔMethanol/ΔCO, and ΔPropane/ΔEthyne ratios than air masses influenced by U.S. emissions, reflecting differences in regional emission signals. The Asian air masses in the eastern Pacific are found to usually be well aged (>5 days), to be highly diffused, and to have low NOy levels. Chemical budget analysis is performed for two flights, and the O3 net chemical budgets are found to be negative (net destructive) in the places dominated by Asian influences or clear sites and positive in polluted American air masses. During the trans-Pacific transport, part of gaseous HNO3 was converted to nitrate particle, and this conversion was attributed to NOy decline. Without the aerosol consideration, the model tends to overestimate HNO3 background concentration along the coast region. At the measurement site of Trinidad Head, northern California, high-concentration pollutants are usually associated with calm wind scenarios, implying that the accumulation of local pollutants leads to the high concentration. Seasonal variations are also discussed from April to May for this site. A high-resolution nesting simulation with 12-km horizontal resolution is used to study the WP-3 flight over Los Angeles and surrounding areas. This nested simulation significantly improved the predictions for emitted and secondary generated species. The difference of photochemical behavior between the coarse (60-km) and nesting simulations is discussed and compared with the observation.

Received 5 January 2004; accepted 10 March 2004; published 9 July 2004.

Keywords: chemical transport model; nesting simulation; atmospheric photochemistry.

Index Terms: 0317 Atmospheric Composition and Structure: Chemical kinetic and photochemical properties; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 3337 Meteorology and Atmospheric Dynamics: Numerical modeling and data assimilation.


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Citation: Tang, Y., et al. (2004), Multiscale simulations of tropospheric chemistry in the eastern Pacific and on the U.S. West Coast during spring 2002, J. Geophys. Res., 109, D23S11, doi:10.1029/2004JD004513.