Multi-scale model analysis of boundary layer ozone over East Asia M. Lin1, T. Holloway1, T. Oki2, D. G. Streets3, and A. Richter4 1Center for Sustainability and the Global Environment, Nelson Institute for Environmental Studies, University of Wisconsin-Madison, Madison, WI, USA 2Institute of Industrial Science, University of Tokyo, Tokyo, Japan 3Argonne National Laboratory, Argonne, IL, USA 4Institute of Environmental Physics, University of Bremen, Bremen, Germany
Abstract. This study employs the regional Community Multiscale Air Quality (CMAQ) model
to examine seasonal and diurnal variations of boundary layer ozone (O3)
over East Asia. We evaluate the response of model simulations of boundary
layer O3 to the choice of chemical mechanisms, meteorological fields,
boundary conditions, and model resolutions. Data obtained from surface
stations, aircraft measurements, and satellites are used to advance
understanding of O3 chemistry and mechanisms over East Asia and
evaluate how well the model represents the observed features.
Satellite measurements and model simulations of summertime rainfall are
used to assess the impact of the Asian monsoon on O3 production. Our
results suggest that summertime O3 over Central Eastern China is highly
sensitive to cloud cover and monsoonal rainfall over this region. Thus,
accurate simulation of the East Asia summer monsoon is critical to model
analysis of atmospheric chemistry over China.
Examination of hourly summertime O3 mixing ratios from sites in Japan
confirms the important role of diurnal boundary layer fluctuations in
controlling ground-level O3. By comparing five different model configurations
with observations at six sites, the specific mechanisms responsible for model
behavior are identified and discussed. In particular, vertical mixing, urban
chemistry, and dry deposition depending on boundary layer height strongly affect
model ability to capture observed behavior.
Central Eastern China appears to be the most sensitive region in our study
to the choice of chemical mechanisms.
Evaluation with TRACE-P aircraft measurements reveals that neither the CB4
nor the SAPRC99 mechanisms consistently capture observed behavior of key
photochemical oxidants in springtime. However, our analysis finds that
SAPRC99 performs somewhat better in simulating mixing ratios of H2O2
(hydrogen peroxide) and PAN (peroxyacetyl nitrate) at flight altitudes below 1 km.
The high level of uncertainty associated with O3 production in Central
Eastern China poses a major problem for regional air quality management.
This highly polluted, densely populated region would greatly benefit from
comprehensive air quality monitoring and the development of model chemical
mechanisms appropriate to this unique atmospheric environment.
Citation: Lin, M., Holloway, T., Oki, T., Streets, D. G., and Richter, A.: Multi-scale model analysis of boundary layer ozone over East Asia, Atmos. Chem. Phys., 9, 3277-3301, doi:10.5194/acp-9-3277-2009, 2009.