scholarly journals Retrospective analysis of 2015–2017 winter-time PM<sub>2.5</sub> in China: response to emission regulations and the role of meteorology

2018 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Junmei Ban ◽  
Pusheng Zhao ◽  
Min Chen
Keyword(s):  
Control Experiment ◽  
Control Strategies ◽  
Emission Control ◽  
Reanalysis Data ◽  
River Delta ◽  
Central China ◽  
Pressure System ◽  
Pollution Dispersion ◽  
Assimilation Experiment ◽  
Winter Time

Abstract. To better characterize the anthropogenic emission relevant aerosol species, the GSI-WRF/Chem data assimilation system was updated from the GOCART aerosol scheme to MOSAIC-4BIN scheme. Three year (2015–2017) winter-time (January) surface PM2.5 observations from 1600&amp;plus; sites were assimilated hourly using the updated 3DVAR system in the assimilation experiment CONC_DA. Parallel control experiment that did not employ DA (NO_DA) was also performed. Both experiments were verified against the surface PM2.5 observations, MODIS 550-nm AOD and also 550-nm AOD at 9 AERONET sites. In the NO_DA experiment using 2010_MEIC emissions, modeled PM2.5 are severely overestimated in Sichuan Basin (SB), Central China (CC), YRD (Yangzi River Delta), and PRD (Pearl River Delta) which indicated the emissions for 2010 are not appropriate for 2015–2017, as strict emission control strategies were implemented in recent years. Meanwhile, underestimations in Northeastern China (NEC) and Xin Jiang (XJ) were also observed. The assimilation experiments significantly reduced the high biases of surface PM2.5 in SB, CC, YRD, and PRD, and also low biases in NEC. However the improvement of the low biases in XJ is relatively small due to the large difference between the observations and the model background in the DA process, likely indicating that the emissions in the model are seriously underestimated in this region. Assimilating surface PM2.5 also significantly changed the column AOD and resulted in closer agreement with MODIS data and observations at AERONET sites. The observations and the reanalysis data from assimilation experiment were used to investigate the year-to-year changes. As the differences of the reanalysis data (CONC_DA) among years reflect combining effects of meteorology and emission and the differences of modeling result from control experiment (NO_DA, with same emissions) among years reflect the separate effect of meteorology, the important roles of emission and meteorology in driving the changes in the three years can be distinguished and analyzed quantitatively. The analysis indicated that meteorology played different roles in 2016 and 2017: the higher pressure system, lower temperature and higher PBLH in 2016 are favorable for pollution dispersion (compared with 2015) while the situation is almost the opposite in 2017 (compared with 2016) that leads to the increasing PM2.5 from 2016 to 2017 although emission control strategy were implemented in both years. There are still large uncertainties in this approach especially the inaccurate emission input in the model brings large biases in the analysis.

scholarly journals Retrospective analysis of 2015–2017 wintertime PM<sub>2.5</sub> in China: response to emission regulations and the role of meteorology

2019 ◽  
Vol 19 (11) ◽  
pp. 7409-7427 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Junmei Ban ◽  
Pusheng Zhao ◽  
Min Chen
Keyword(s):  
Data Assimilation ◽  
Control Strategies ◽  
Dominant Role ◽  
Fine Particulate Matter ◽  
Emission Control ◽  
River Delta ◽  
Control Measures ◽  
Central China ◽  
Assimilation Experiment

Abstract. To better characterize anthropogenic emission-relevant aerosol species, the Gridpoint Statistical Interpolation (GSI) and Weather Research and Forecasting with Chemistry (WRF/Chem) data assimilation system was updated from the GOCART aerosol scheme to the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) 4-bin (MOSAIC-4BIN) aerosol scheme. Three years (2015–2017) of wintertime (January) surface PM2.5 (fine particulate matter with an aerodynamic diameter smaller than 2.5 µm) observations from more than 1600 sites were assimilated hourly using the updated three-dimensional variational (3DVAR) system. In the control experiment (without assimilation) using Multi-resolution Emission Inventory for China 2010 (MEIC_2010) emissions, the modeled January averaged PM2.5 concentrations were severely overestimated in the Sichuan Basin, central China, the Yangtze River Delta and the Pearl River Delta by 98–134, 46–101, 32–59 and 19–60 µg m−3, respectively, indicating that the emissions for 2010 are not appropriate for 2015–2017, as strict emission control strategies were implemented in recent years. Meanwhile, underestimations of 11–12, 53–96 and 22–40 µg m−3 were observed in northeastern China, Xinjiang and the Energy Golden Triangle, respectively. The assimilation experiment significantly reduced both high and low biases to within ±5 µg m−3. The observations and the reanalysis data from the assimilation experiment were used to investigate the year-to-year changes and the driving factors. The role of emissions was obtained by subtracting the meteorological impacts (by control experiments) from the total combined differences (by assimilation experiments). The results show a reduction in PM2.5 of approximately 15 µg m−3 for the month of January from 2015 to 2016 in the North China Plain (NCP), but meteorology played the dominant role (contributing a reduction of approximately 12 µg m−3). The change (for January) from 2016 to 2017 in NCP was different; meteorology caused an increase in PM2.5 of approximately 23 µg m−3, while emission control measures caused a decrease of 8 µg m−3, and the combined effects still showed a PM2.5 increase for that region. The analysis confirmed that emission control strategies were indeed implemented and emissions were reduced in both years. Using a data assimilation approach, this study helps identify the reasons why emission control strategies may or may not have an immediately visible impact. There are still large uncertainties in this approach, especially the inaccurate emission inputs, and neglecting aerosol–meteorology feedbacks in the model can generate large uncertainties in the analysis as well.

scholarly journals Effectiveness of emission control in reducing PM<sub>2.5</sub> pollution in central China during winter haze episodes under various potential synoptic controls

2021 ◽  
Vol 21 (4) ◽  
pp. 3143-3162
Author(s):  
Yingying Yan ◽  
Yue Zhou ◽  
Shaofei Kong ◽  
Jintai Lin ◽  
Jian Wu ◽  
...  
Keyword(s):  
Southern China ◽  
Global Analysis ◽  
Surface Wind ◽  
Emission Control ◽  
Central China ◽  
Emission Sources ◽  
Pressure System ◽  
Haze Pollution ◽  
Synoptic Conditions ◽  
Local Emission

Abstract. Currently, mitigating severe particle pollution in autumn and winter is the key to further improving the air quality of China. The source contributions and transboundary transport of fine particles (PM2.5) in pollution episodes are closely related to large-scale or synoptic-scale atmospheric circulation. How to effectively reduce emissions to control haze pollution under different synoptic conditions is rarely reported. In this study, we classify the synoptic conditions over central China from 2013 to 2018 by using Lamb–Jenkinson method and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Final (FNL) operational global analysis data. The effectiveness of emission control to reduce PM2.5 pollution during winter haze episodes under potential synoptic controls is simulated by GEOS-Chem model. Among the 10 identified synoptic patterns, four types account for 87 % of the total pollution days. Two typical synoptic modes are characterized by low surface wind speed and stable weather conditions or high relative humidity (A or C type) over central China due to a high-pressure system or a southwest trough and low-pressure system, blocking pollutants dispersion. Sensitivity simulations show that these two heavy pollution processes are mainly contributed by local emission sources with ∼82 % for A type and ∼85 % for C type, respectively. The other two patterns lead to pollution of transport characteristics affected by northerly or southerly winds (NW or SW type), carrying air pollution from northern or southern China to central China. The contribution of pollution transmission from northern and southern China is 36.9 % and 7.6 %, respectively of PM2.5, and local emission sources contribute 41 % and 69 %, respectively. We also estimate the effectiveness of emission reduction in these four typical severe pollution synoptic processes. By only reducing SO2 and NOx emission and not controlling NH3, the enhanced nitrate counteracts the effect of sulfate reduction on PM2.5 mitigation, with a less than 4 % decrease in PM2.5. In addition, to effectively mitigate haze pollution of NW- and SW-type synoptic-controlled episodes, local emission control actions should be in coordination with regional collaborative actions.

scholarly journals Contrasting chemical environments in summertime for atmospheric ozone across major Chinese industrial regions: the effectiveness of emission control strategies

2021 ◽  
Author(s):  
Zhenze Liu ◽  
Ruth M. Doherty ◽  
Oliver Wild ◽  
Michael Hollaway ◽  
Fiona M. O'Connor
Keyword(s):  
Climate Model ◽  
Control Strategies ◽  
Regional Scale ◽  
Emission Control ◽  
Response Surfaces ◽  
River Delta ◽  
Nox Emissions ◽  
Voc Emissions ◽  
Industrial Regions ◽  
Surface O3

Abstract. The UKCA chemistry-climate model is used to quantify the differences in chemical environment for surface O3 for six major industrial regions across China in summer 2016. We first enhance the UKCA gas-phase chemistry scheme by incorporating reactive VOC tracers that are necessary to represent urban and regional-scale O3 photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface O3 concentrations across these regions well. Simulated O3 concentrations are highest in Beijing and Shijiazhuang on the North China Plain and in Chongqing, lower in Shanghai and Nanjing in the Yangtze River Delta, and lowest in Guangzhou in the Pearl River Delta despite the highest daytime O3 production rates in Guangzhou. NOx / VOC and H2O2 / HNO3 ratios indicate that O3 production across all regions except Chongqing is VOC limited. We confirm this by constructing O3 response surfaces for each region changing NOx and VOC emissions and further contrast the effectiveness of measures to reduce surface O3 concentrations. In VOC limited regions, reducing NOx emissions by 20 % leads to a substantial O3 increase (11 %) in Shanghai. We find that reductions in NOx emissions alone of more than 70 % are required to decrease O3 concentrations across all regions. Reductions in VOC emissions alone of 20 % produce the largest decrease (−11 %) in O3 levels in Shanghai and Guangzhou and the smallest decrease (−1 %) in Chongqing. These responses are substantially different from those currently found in highly populated regions in other parts of the world, likely due to higher NOx emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface O3 pollution in these major industrial regions, and emphasizes that combined NOx and VOC emission controls play a pivotal role in effectively offsetting high O3 levels. It also demonstrates new capabilities in capturing regional air pollution that will permit this model to be used for future studies of regional air quality-climate interactions.

scholarly journals Contrasting chemical environments in summertime for atmospheric ozone across major Chinese industrial regions: the effectiveness of emission control strategies

2021 ◽  
Vol 21 (13) ◽  
pp. 10689-10706
Author(s):  
Zhenze Liu ◽  
Ruth M. Doherty ◽  
Oliver Wild ◽  
Michael Hollaway ◽  
Fiona M. O’Connor
Keyword(s):  
Climate Model ◽  
Control Strategies ◽  
Regional Scale ◽  
Emission Control ◽  
Response Surfaces ◽  
River Delta ◽  
Nox Emissions ◽  
Voc Emissions ◽  
Industrial Regions ◽  
Surface O3

Abstract. The United Kingdom Chemistry and Aerosols (UKCA) chemistry–climate model is used to quantify the differences in chemical environment for surface O3 for six major industrial regions across China in summer 2016. We first enhance the UKCA gas-phase chemistry scheme by incorporating reactive volatile organic compound (VOC) tracers that are necessary to represent urban and regional-scale O3 photochemistry. We demonstrate that the model with the improved chemistry scheme captures the observed magnitudes and diurnal patterns of surface O3 concentrations across these regions well. Simulated O3 concentrations are highest in Beijing and Shijiazhuang on the North China Plain and in Chongqing, lower in Shanghai and Nanjing in the Yangtze River Delta, and lowest in Guangzhou in the Pearl River Delta despite the highest daytime O3 production rates in Guangzhou. NOx / VOC and H2O2 / HNO3 ratios indicate that O3 production across all regions except Chongqing is VOC limited. We confirm this by constructing O3 response surfaces for each region changing NOx and VOC emissions and further contrast the effectiveness of measures to reduce surface O3 concentrations. In VOC-limited regions, reducing NOx emissions by 20 % leads to a substantial O3 increase (11 %) in Shanghai. We find that reductions in NOx emissions alone of more than 70 % are required to decrease O3 concentrations across all regions. Reductions in VOC emissions alone of 20 % produce the largest decrease (−11 %) in O3 levels in Shanghai and Guangzhou and the smallest decrease (−1 %) in Chongqing. These responses are substantially different from those currently found in highly populated regions in other parts of the world, likely due to higher NOx emission levels in these Chinese regions. Our work provides an assessment of the effectiveness of emission control strategies to mitigate surface O3 pollution in these major industrial regions and emphasises that combined NOx and VOC emission controls play a pivotal role in effectively offsetting high O3 levels. It also demonstrates new capabilities in capturing regional air pollution that will permit this model to be used for future studies of regional air-quality–climate interactions.

scholarly journals Effectiveness of emission control to reduce PM<sub>2.5</sub> pollution of Central China during winter haze episodes under various potential synoptic controls

2020 ◽  
Author(s):  
Yingying Yan ◽  
Yue Zhou ◽  
Shaofei Kong ◽  
Jintai Lin ◽  
Jian Wu ◽  
...  
Keyword(s):  
Global Analysis ◽  
Surface Wind ◽  
Emission Control ◽  
Central China ◽  
Emission Sources ◽  
Pressure System ◽  
Small Surface ◽  
Haze Pollution ◽  
Synoptic Conditions ◽  
Local Emission

Abstract. Currently solving the severe particle pollution in autumn and winter is the key to further improve the air quality of China. The source contributions and transboundary transport of fine particles (PM2.5) in pollution episodes are closely related to large-scale or synoptic-scale atmospheric circulation. Under different synoptic conditions, how to effectively reduce emissions to control haze pollution is rarely reported. In this study, we classify the synoptic conditions over Central China from 2013 to 2018 by using Lamb-Jenkension method and the NCEP/NCAR FNL operational global analysis data. The effectiveness of emission control to reduce PM2.5 pollution during winter haze episodes under potential synoptic controls is simulated by GEOS-Chem model. Among the ten identified synoptic patterns, four types account for 87 % of the total pollution days. Two typical synoptic modes of them are characterized by small surface wind speed and stable weather conditions/high relative humidity (A/C-type) over Central China due to a high-pressure system/a southwest trough low-pressure system, blocking pollutants dispersion. Sensitivity simulations show that these two heavy pollution processes are mainly contributed by local emission sources with ~82 % for A-type and ~85 % for C-type, respectively. The other two patterns lead to pollution of transportation characteristics affected by northerly/southerly winds (NW/SW-type), carrying air pollution from northern/southern China to Central China. The contribution of pollution transportation from North/South China is 36.9 %/7.6 % of PM2.5 and local emission sources contribute 41 %/69 %. We also estimate the effectiveness of emission reduction in these four typical severe pollution synoptic processes. By only reducing SO2 and NOx emission and not controlling NH3, the enhanced nitrate counteracts the effect of sulfate reduction on PM2.5 mitigations with less than 4% decrease in PM2.5. In addition, to effectively mitigate haze pollution in NW/SW-type synoptic controlled episodes, local emission control actions should be in coordination with regional collaborative actions.

scholarly journals 2015 and 2016 winter-time air pollution in China: SO<sub>2</sub> emission changes derived from a WRF/Chem-EnKF coupled data assimilation system

2019 ◽  
Author(s):  
Dan Chen ◽  
Zhiquan Liu ◽  
Junmei Ban ◽  
Min Chen
Keyword(s):  
Data Assimilation ◽  
Emission Reduction ◽  
Emission Inventory ◽  
Southern China ◽  
Control Strategies ◽  
River Delta ◽  
Central China ◽  
Western China ◽  
Data Assimilation System ◽  
Assimilation System

Abstract. Ambient pollutants in China changes significantly in recent years due to strict control strategies implemented by the government. The control strategies also bring uncertainties to both the bottom-up emission inventory and the model-ready gridded emission inputs especially in winter season. In this study, we updated the WRF/Chem-EnKF Data Assimilation system to quantitatively estimate the gridded hourly SO2 emissions using hourly surface observations as constraints. Different from our previous study, in which meteorology and emission were both perturbed to obtain larger spread aiming to improve forecast skills; in this study, only emission was perturbed to ensure analyzed emission purely reflect necessary adjustments due to the emission uncertainties. In addition, direct emissions instead of emission scaling factors were used as analysis variable, which allowed for the detection of new emission sources. 2010 MEIC emission inventory (for January) was used as priori to generate 2015 and 2016 January analyzed emissions. The SO2 emission changing trends for northern, western and southern China from 2010 to 2015 and that from 2015 to 2016 (for the month of January) were investigated. The January 2010–2015 differences showed inhomogeneous change patterns in different regions: (1) significant emission reduction in southern China, (2) significant emission reduction in larger cities but widely increase in surrounding suburban and rural regions for northern China which may indicate the missing raw coal combustion for winter heating that not taken into account in the priori emission inventory; (3) significantly large emission increase in western China due to the energy expansion strategy. This not only reflected the changes during the five years, but also combined the uncertainties in the priori emissions. The January 2015–2016 differences showed widely emission reduction from 2015 to 2016, indicating the stricter control strategy fully executed nationwide. These changes were corresponded to facts in reality, indicating that the updated DA system was capable to detect the emission deficiencies and optimize the emission. By generating the hourly analyzed emissions, the diurnal pattern of emissions (in terms of hourly factors) were also obtained. Forecast experiments showed the improvements by using analyzed emissions were much larger in southern China than that in northern and western China. For Sichuan Basin, Central China, Yangzi River Delta, and Pearl River Delta, BIAS and RMSE decreased by 61.8 %–78.2 % and 27.9 %–52.2 %, respectively, and correlation coefficients increased by 12.5 %–47.1 %. However, the improvement in northern and western China were limited due to small spread. Another limitation of the study is that the analyzed emissions are still model dependent, as the ensembles are conducted through WRF/Chem model and thus the performances of ensembles are model dependent.

scholarly journals The effects of energy paths and emission controls and standards on future trends in China's emissions of primary air pollutants

2014 ◽  
Vol 14 (17) ◽  
pp. 8849-8868 ◽  
Author(s):  
Y. Zhao ◽  
J. Zhang ◽  
C. P. Nielsen
Keyword(s):  
Air Pollutants ◽  
Control Strategies ◽  
Emission Control ◽  
Pollution Prevention ◽  
Air Pollutant ◽  
Pollutant Emissions ◽  
Carbonaceous Aerosols ◽  
Emission Controls ◽  
Control Devices ◽  
Anthropogenic Pollutant

Abstract. To examine the efficacy of China's actions to control atmospheric pollution, three levels of growth of energy consumption and three levels of implementation of emission controls are estimated, generating a total of nine combined activity-emission control scenarios that are then used to estimate trends of national emissions of primary air pollutants through 2030. The emission control strategies are expected to have more effects than the energy paths on the future emission trends for all the concerned pollutants. As recently promulgated national action plans of air pollution prevention and control (NAPAPPC) are implemented, China's anthropogenic pollutant emissions should decline. For example, the emissions of SO2, NOx, total suspended particles (TSP), PM10, and PM2.5 are estimated to decline 7, 20, 41, 34, and 31% from 2010 to 2030, respectively, in the "best guess" scenario that includes national commitment of energy saving policy and implementation of NAPAPPC. Should the issued/proposed emission standards be fully achieved, a less likely scenario, annual emissions would be further reduced, ranging from 17 (for primary PM2.5) to 29% (for NOx) declines in 2015, and the analogue numbers would be 12 and 24% in 2030. The uncertainties of emission projections result mainly from the uncertain operational conditions of swiftly proliferating air pollutant control devices and lack of detailed information about emission control plans by region. The predicted emission trends by sector and chemical species raise concerns about current pollution control strategies: the potential for emissions abatement in key sectors may be declining due to the near saturation of emission control devices use; risks of ecosystem acidification could rise because emissions of alkaline base cations may be declining faster than those of SO2; and radiative forcing could rise because emissions of positive-forcing carbonaceous aerosols may decline more slowly than those of SO2 emissions and thereby concentrations of negative-forcing sulfate particles. Expanded control of emissions of fine particles and carbonaceous aerosols from small industrial and residential sources is recommended, and a more comprehensive emission control strategy targeting a wider range of pollutants (volatile organic compounds, NH3 and CO, etc.) and taking account of more diverse environmental impacts is also urgently needed.

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