Intensified modulation of winter aerosol pollution in China by El Niño with short duration

Ren

et al. 2022

Nat Commun

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Record rainfall and severe flooding struck eastern China in the summer of 2020. The extreme summer rainfall occurred during the COVID-19 pandemic, which started in China in early 2020 and spread rapidly across the globe. By disrupting human activities, substantial reductions in anthropogenic emissions of greenhouse gases and aerosols might have affected regional precipitation in many ways. Here, we investigate such connections and show that the abrupt emissions reductions during the pandemic strengthened the summer atmospheric convection over eastern China, resulting in a positive sea level pressure anomaly over northwestern Pacific Ocean. The latter enhanced moisture convergence to eastern China and further intensified rainfall in that region. Modeling experiments show that the reduction in aerosols had a stronger impact on precipitation than the decrease of greenhouse gases did. We conclude that through abrupt emissions reductions, the COVID-19 pandemic contributed importantly to the 2020 extreme summer rainfall in eastern China.

Section: Discussionmentioning

confidence: 99%

Abrupt emissions reductions during COVID-19 contributed to record summer rainfall in China

Ren

et al. 2022

Nat Commun

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“…The pure ENSO influences can be more cleanly isolated using general circulation models driven by prescribed SSTs with and without ENSO signal (Zeng et al 2021). The composite differences in meteorological parameters between El Niño and La Niña years from MERRA-2 reanalysis are validated here by comparing with ERA5 reanalysis (figure S7).…”

Section: Conclusion and Discussionmentioning

confidence: 96%

ENSO modulation of summertime tropospheric ozone over China

Wang

et al. 2022

Environ. Res. Lett.

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Ozone (O3) is one of the most critical pollutants affecting air quality in China in recent years. In this study, different impacts of the El Niño–Southern Oscillation (ENSO) warm/cold phases on summertime tropospheric O3 over China are examined based on model simulations, ground measurements, and reanalysis data. Summertime surface O3 concentrations in China show a positive correlation with ENSO index during years 1990–2019, with the largest increases by 20% over southern China in El Niño (warm phase) relative to La Niña (cold phase) years. The ENSO modulation extends to the middle and even upper troposphere. Our analysis indicates that O3 flux convergence associated with weakened southerlies is the primary reason for the increase in tropospheric O3 over southern China. In addition, the O3 increase during El Niño years is mainly from domestic emissions in China. This study highlights the potential significance of ENSO in modulating tropospheric O3 concentrations in China, with great implications for O3 pollution mitigation.

“…AClean: same as Base, but anthropogenic emissions of aerosols and precursors over China are fixed at year 2017. concentration decreases with maximum decreases in the range of 12-18 μg m -3 . The low biases in CAM6 are caused by many factors including the lack of nitrate and ammonium representation, the absence of natural aerosols in the calculation of modeled PM2.5 concentrations, strong aerosol wet removal, and uncertainties in new particle formation, which have been reported in many previous studies (Yang et al, 2017a, b;Zeng et al, 2021;Ren et al, 2021). The model generally captures the percentage decreases in PM2.5 concentrations by about 20-40% in seven sub-regions over central-eastern China (Fig.…”

Section: Methodsmentioning

confidence: 88%

“…To mitigate the serious air pollution, China issued the Air Pollution Prevention and Control Action Plan in 2013 (Clean Air Alliance of China , 2013), in which a decrease in PM2.5 (PM with diameter less than 2.5 μm) by 15%-25% by year 2017, compared to 2013, was proposed for various regions of China. The emissions of major air pollutants have been reduced since then and aerosol concentrations have substantially decreased across China (Li et al, 2021). In 74 key cities in China, the annual average of observed PM2.5 concentrations decreased by 33.3% from 2013 to 2017 (Huang et al, 2018).…”

mentioning

confidence: 99%

Climate impacts of emission reductions in China during 2013–2017

Gao

Wang

et al. 2022

Preprint

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Abstract. China has implemented a sequence of policies for clean air since year 2013 and the aerosol pollution has been substantially improved, but ozone (O3) related issues arose. Here, climate responses to changes in aerosols and O3 related to the emission reductions over China during 2013–2017 are investigated using the Community Earth System Model version 2 (CESM2). The overall decreases in aerosols produced an anomalous warming of 0.09 ± 0.10 °C in eastern China (22° N–40° N, 110° E–122.5° E), which is further enhanced by the increase in O3 in the lower troposphere, resulting in an accelerated warming of 0.16 ± 0.15 °C in eastern China. Reductions in industrial emissions contributed the most to the aerosol-induced warming, while emission reductions from residential sector induced a cooling effect due to a substantial decrease in light-absorbing black carbon aerosols. It implies that switching residential sector to cleaner energy is more effective to achieve climate and health co-benefits in China.