Abstract
Multiscale simulations of tropospheric chemistry in the eastern Pacific and on the U.S. West Coast during spring 2002
Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA
Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA
Geophysical Fluid Dynamics Laboratory, NOAA, Princeton, New Jersey, USA
Research Institute for Applied Mechanics, Kyushu University, Fukuoka, Japan
Center for Global and Regional Environmental Research, University of Iowa, Iowa City, Iowa, USA
Decision and Information Sciences Division, Argonne National Laboratory, Argonne, Illinois, USA
Department of Mechanical and Aerospace Engineering, University of California, Irvine, California, USA
Department of Ecological Engineering, Toyohashi University of Technology, Toyohashi, Japan
Department of Computer Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
Department of Physics, University of Manchester Institute of Science and Technology, Manchester, UK
National Center for Atmospheric Research, Boulder, Colorado, USA
National Center for Atmospheric Research, Boulder, Colorado, USA
School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
Aeronomy Laboratory, NOAA, Boulder, Colorado, USA
Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
Pacific Marine Environmental Laboratory, NOAA, Seattle, Washington, USA
Aeronomy Laboratory, NOAA, Boulder, Colorado, USA
Aerodyne Research Inc., Billerica, Massachusetts, USA
Department of Environmental Science, Policy, and Management, University of California, Berkeley, California, USA
National Center for Atmospheric Research, Boulder, Colorado, USA
National Center for Atmospheric Research, Boulder, Colorado, USA
National Center for Atmospheric Research, Boulder, Colorado, USA
National Center for Atmospheric Research, Boulder, Colorado, USA
NASA Langley Research Center, Hampton, Virginia, USA
NASA Ames Research Center, Moffett Field, California, USA
National Center for Atmospheric Research, Boulder, Colorado, USA
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.
Citation: (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.
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