To illuminate the issue of trans-boundary O 3 pollution and regional O 3 reduction policies in East Asia, we have investigated the East Asian ozone (O 3) response to perturbations caused by Chinese anthropogenic emissions using the Community Multiscale Air Quality (CMAQ) model, a regional chemical transport model. The O 3 responses have been examined for the range between -100 and +100% changes from the Chinese emissions level in 2004 in 10% intervals. We have found that springtime and summertime O 3 responses both at the source and at the downwind areas can be regarded as linear over the range between -30 and +100% changes from the current emissions level. We therefore suggest that the perturbation between -30 and +100% is sufficiently small to avoid nonlinear chemical influence on O 3 formation in a model experiment to investigate East Asian scale O 3 source-receptor relationships. On the other hand, the O 3 response is strongly nonlinear in April at Hong Kong, where the current NMVOCs/NO x ratio is low and the O 3 production regime is easily moved to the NMVOCs sensitive region. The O 3 responses to the NO x emission changes have been investigated using surface O 3 concentrations at remote Japanese sites and tropospheric NO 2 vertical column density (NO 2 VCD) over central east China both with observations and with model simulations in springtime during 2003-2009. Analysis of satellite data shows that the observed range of NO 2 VCD over central east China in 2003-2009 is the range between -25 and +34% from the 2004 level, which corresponds approximately to an emission variation between -21 and +29%. The O 3 concentration in the downwind region during 2003-2009 responds linearly to a change of the NO 2 VCD over central east China both in the model and in the observation. The corresponding O 3 responses derived from surface observations at remote Japanese sites show linear features consistent with this expectation. The doubling of emissions, i.e., approximately 1.9-fold increase in the NO 2 VCD from 2004, leads to O 3 increments of 5ppbv and 8ppbv in the model and in the observation, respectively. The modeled O 3 increase due to changes in NO x emission explains approximately 60% of the observed O 3 trend at remote Japanese sites. Thus, approximately 40% of the observed O 3 increase is unaccounted for by the NO x emissions growth.
All Science Journal Classification (ASJC) codes
- Environmental Science(all)
- Atmospheric Science