Abstract. Surface ozone is a major pollutant in eastern China, especially during the
summer season. The formation of surface ozone pollution highly depends on
meteorological conditions largely controlled by regional circulation
patterns which can modulate ozone concentrations by influencing the
emission of the precursors, the chemical production rates, and regional
transport. Here we show that summertime ozone pollution over eastern China
is distinctly modulated by the variability of the western Pacific subtropical high
(WPSH), a major synoptic system that controls the summertime weather
conditions of East Asia. Composite and regression analyses indicate that
a positive WPSH anomaly is associated with higher than normal surface ozone
concentration over northern China but lower ozone over southern China.
Stronger than normal WPSH leads to higher temperatures, stronger solar
radiation at the land surface, lower relative humidity, and less
precipitation in northern China, favoring the production and accumulation of
surface ozone. In contrast, all meteorological variables show reverse
changes in southern China under a stronger WPSH. GEOS-Chem simulations
reasonably reproduce the observed ozone changes associated with the WPSH and
support the statistical analyses. We further conduct a budget diagnosis to
quantify the detailed contributions of chemistry, transport, mixing, and
convection processes. The result shows that chemistry plays a decisive role
in leading the ozone changes among these processes. Results show that the
changes in ozone are primarily attributed to chemical processes. Moreover,
the natural emission of precursors from biogenic and soil sources, a major
component influencing the chemical production, accounts for ∼ 30 % of the total surface ozone changes.
Review of “Impact of western pacific subtropical high on ozone pollution over eastern china”
