Keywords:tropospheric ozone, chemical transport model, source-receptor relationship, intercontinental transport
Ozone (O3) near the surface is harmful to human health and to vegetation including crops. It is recognized that intercontinental transport of air pollutants affects air quality over a region. Task Force on Hemispheric Transport of Air Pollutants (TF HTAP) coordinated a multi-model inter-comparison of 21 chemical transport models (CTMs) for assessing source-receptor relationships (i.e., the change in pollutants over a receptor region produced by change in emissions in a source region). Typical horizontal resolution of HTAP models was about 300 km. A coarse-resolution model tends to overpredict ozone chemical production (e.g., Wild and Prather, 2006). However, it is unclear how model horizontal resolution affects source-receptor relationships of tropospheric ozone. We estimated source-receptor relationships of tropospheric ozone using the CHASER global CTM (Sudo et al., 2002) with medium-resolution (T42; 2.8 deg. x 2.8 deg.) and high-resolution (T106; 1.1 deg. x 1.1 deg.). The CHASER model is also developed as an atmospheric chemistry component of the MIROC-ESM-CHEM earth system model, and simulates detailed chemistry in the troposphere and the stratosphere with aerosols simultaneously. We conducted a 2010 control simulation and a sensitivity simulation with 20% reduced emissions in East Asia to estimate source-receptor relationships. The model results show that 20% East Asian emission reductions decrease surface O3 by 0.94 ppbv and by 0.75 ppbv over East Asia in spring respectively in the medium-resolution and high-resolution models. The East Asian emission perturbations also reduced surface O3 by 0.27 ppbv and by 0.24 ppbv in spring over North America respectively in the medium-resolution and the high-resolution models. Our results suggest that the high-resolution model tends to predict smaller decreases in surface O3 over East Asia and North America in response to the East Asian emission reductions.
Wild and Prather (2006), J. Geophys. Res., 111, D11305, doi:10.1029/2005JD006605.
Sudo et al. (2002), J. Geophys. Res., 107, 10.1029/2001JD001113.