Aerosols
Aerosols cut winter ozone but raise it in summer
Open access · cc by · source: Europe PMC
Aerosol haze over China changes ozone in opposite directions in January and July by altering mixing and sunlight.
Key findings
Including aerosol direct effects reduced high winter ozone bias and low summer bias. In January, combined effects cut daily-max ozone by up to 39 μg m−3; in July they raised it by up to 4 μg m−3, mainly via more stable, precursor-rich boundary layers. Photolysis cuts ozone in winter but can raise noon ozone in summer because unused morning precursors react later.
Methodology
Three WRF-CMAQ runs for January and July 2013 turned aerosol radiation feedbacks on or off. Differences isolated photolysis versus dynamical pathways. Process rates and ozone were checked against observations from 74 Chinese cities.
Limitations
Heterogeneous N2O5 chemistry is not quantified. Two months in 2013 cannot represent all years. Urban monitors may not represent rural ozone, and PM2.5–ozone correlations mix chemistry with shared sources.
How this study connects
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