arXiv subjects

Yafang Cheng

Publications and source records attributed to Yafang Cheng.

4 recordsLinked to original sources

arXiv2026

Deep learning reveals a stronger fossil fuel influence than biomass burning in shaping remote tropospheric ozone

Tropospheric ozone (O3) is a key greenhouse gas and atmospheric oxidant, yet its sources in the remote troposphere remain strongly debated. Observation-based tracer analyses suggest that O3 attributed to biomass burning is much greater than that from fossil fuel sources (by a factor of ~2-10), contradicting state-of-the-art global models. Here we show that this discrepancy primarily arises from the strong sensitivity of tracer methods to differences in tracer lifetimes, especially after extended transport to the remote regions. To resolve this discrepancy, we develop a deep learning (DL) framework that synthesizes global observations and chemical transport model simulations. The DL approach accurately infers source contributions and reveals that fossil fuel emissions contribute over three times more O3 to the remote troposphere than biomass burning. Our findings underscore that phasing out fossil fuels remains the most powerful lever for mitigating remote tropospheric ozone.

physics.ao-ph↗

arXiv2024

Multiphase buffering by ammonia sustains sulfate production in atmospheric aerosols

Multiphase oxidation of sulfur dioxide (SO2) is an important source of sulfate in the atmosphere. There are, however, concerns that protons produced during SO2 oxidation may cause rapid acidification of aerosol water and thereby quickly shut down the fast reactions favored at high pH. Here, we show that the sustainability of sulfate production is controlled by the competing effects of multiphase buffering and acidification, which can be well described by a characteristic buffering time, {\tau}buff. We find that globally, {\tau}buff is long enough (days) to sustain sulfate production over most populated regions, where the acidification of aerosol water is counteracted by the strong buffering effect of NH4+/NH3. Our results highlight the importance of anthropogenic ammonia emissions and pervasive human influences in shaping the chemical environment of the atmosphere.

physics.ao-ph↗

arXiv2020

Spring Festival points the way to cleaner air in China

Human migration during the Chinese Spring Festival (SF) is the largest collective human activity of its kind in the modern era-involving about one-tenth of the world population and over six percent of the earth's land surface area. The festival results in a drop of air pollutant emissions that causes dramatic changes of atmospheric composition over China's most polluted regions. Based on satellite and in-situ measurements for the years 2005-2019 over 50 cities in eastern China, we find that the atmospheric NO2 pollution dropped by ~40% during the SF week, and fine particulate matter (PM2.5) decreased by ~30% in the following week, reflecting the effectiveness of precursor emission controls on the mitigation of secondary PM2.5 formation. However, although human activity and emissions are at the lowest level, air pollution over eastern China during the SF still far exceeds that over other worldwide pollution hotspots. Our analyses suggest that measures based solely on end-of-pipe controls and industry upgrades may not suffice to meet air quality goals. Further cleaning of the air in China depends fundamentally on sustainable advances in both heavy industry upgrades and clean energy transition.

physics.ao-ph↗

arXiv2020

Natural gas shortages during the "coal-to-gas" transition in China have caused a large redistribution of air pollution

The Chinese "coal-to-gas" strategy aims at reducing coal consumption and related air pollution by promoting the use of clean and low carbon fuels in northern China. Here we show that on top of meteorological influences, these measures achieved an average decrease of fine particulate matter (PM2.5) concentrations of ~14% during winter 2017 in Beijing and surrounding areas (the "2+26" pilot cities). However, the localized air quality improvement was accompanied by a contemporaneous ~15% upsurge of PM2.5 concentrations over large areas in southern China. We find that the pollution transfer that resulted from a shift in emissions was caused by a natural gas shortage in the south due to the "coal-to-gas" transition in the north. The overall shortage of natural gas greatly jeopardized the air quality benefits of the "coal-to-gas" strategy in winter 2017 and reflects structural challenges and potential threats in China's clean energy transition.

physics.ao-ph↗