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. Currently, mitigating severe particle pollution in autumn and winter isthe key to further improving the air quality of China. The sourcecontributions and transboundary transport of fine particles(PM2.5) in pollution episodes are closely related to large-scaleor synoptic-scale atmospheric circulation. How to effectively reduce emissions to control haze pollution under different synopticconditions israrely reported. In this study, we classify the synoptic conditions overcentral China from 2013 to 2018 by using Lamb–Jenkinson method and theNational Centers for Environmental Prediction/National Center forAtmospheric Research (NCEP/NCAR) Final (FNL) operational global analysis data. The effectiveness ofemission control to reduce PM2.5 pollution during winter haze episodesunder potential synoptic controls is simulated by GEOS-Chem model. Among the10 identified synoptic patterns, four types account for 87 % of the totalpollution days. Two typical synoptic modes are characterized bylow surface wind speed and stable weather conditions or high relativehumidity (A or C type) over central China due to a high-pressure system or asouthwest trough and low-pressure system, blocking pollutants dispersion.Sensitivity simulations show that these two heavy pollution processes aremainly contributed by local emission sources with ∼82 % forA type and ∼85 % for C type, respectively. The other twopatterns lead to pollution of transport characteristics affected bynortherly or southerly winds (NW or SW type), carrying air pollution fromnorthern or southern China to central China. The contribution of pollutiontransmission from northern and southern China is 36.9 % and 7.6 %, respectively of PM2.5, andlocal emission sources contribute 41 % and 69 %, respectively. We also estimate theeffectiveness of emission reduction in these four typical severe pollutionsynoptic processes. By only reducing SO2 and NOx emission and notcontrolling NH3, the enhanced nitrate counteracts the effect of sulfatereduction on PM2.5 mitigation, with a less than 4 % decrease inPM2.5. In addition, to effectively mitigate haze pollution ofNW- and SW-type synoptic-controlled episodes, local emission control actionsshould be in coordination with regional collaborative actions.

atmospheric chemistry and physics

Effectiveness of emission control in reducing PM&amp;lt;sub&amp;gt;2.5&amp;lt;/sub&amp;gt; pollution in central China during winter haze episodes under various potential synoptic controls