Abstract. Previous studies have emphasized that the decrease in
photolysis rate at the surface induced by the light extinction of aerosols
could weaken ozone photochemistry and then reduce surface ozone. However,
quantitative studies have shown that weakened photochemistry leads to a much
greater reduction in the net chemical production of ozone, which does not
match the reduction in surface ozone. This suggests that in addition to
photochemistry, some other physical processes related to the variation of
ozone should also be considered. In this study, the Weather Research and
Forecasting with Chemistry (WRF-Chem) model coupled with the ozone source
apportionment method was applied to determine the mechanism of ozone
reduction induced by aerosols over central East China (CEC). Our results
showed that weakened ozone photochemistry led to a significant reduction in
ozone net chemical production, which occurred not only at the surface but
also within the lowest several hundred meters in the planetary boundary
layer (PBL). Meanwhile, a larger ozone gradient was formed in the vertical
direction, which led to the high concentrations of ozone aloft being
entrained by turbulence from the top of the PBL to the surface and partly
counteracting the reduction in surface ozone. In addition, contribution from
dry deposition was weakened due to the decrease in surface ozone
concentration. The reduction in the ozone's sink also slowed down the
rate of the decrease in surface ozone. Ozone in the upper layer of the
PBL was also reduced, which was induced by much ozone aloft being entrained
downward. Therefore, by affecting the photolysis rate, the impact of
aerosols was a reduction in ozone not only at the surface but also
throughout the entire PBL during the daytime over CEC in this study. The
ozone source apportionment results showed that 41.4 %–66.3 % of the
reduction in surface ozone came from local and adjacent source regions,
which suggested that the impact of aerosols on ozone from local and adjacent
regions was more significant than that from long-distance regions. The
results also suggested that while controlling the concentration of aerosols,
simultaneously controlling ozone precursors from local and adjacent source
regions is an effective way to suppress the increase in surface ozone over
CEC at present.