Simulations of Sulfate-Nitrate-Ammonium (SNA) aerosols during the extreme haze events over Northern China in October 2014

Chen, D.; Liu, Z.; Fast, Jerome D.; Ban, Jihee

doi:10.5194/acp-2016-222

Cited by 21 publications

(41 citation statements)

References 19 publications

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“…In this study, the interfaced air quality model is WRF-Chem. The WRF-Chem settings are very similar to those of Chen et al (2016). Here, only a brief summary of the model configuration and observations is provided below.…”

Section: Model Description Observations and Methodologymentioning

confidence: 99%

“…As in Chen et al (2016), version 3.6.1 of the WRF-Chem model is used in this study to simulate the aerosols and gas-phase chemistry processes. A summary of the used physical parameterizations is given in Table 1.…”

Section: Wrf-chem Model and Emissionsmentioning

confidence: 99%

“…In result, the MOSAIC scheme exhibits a better performance in representing the complex PM2.5 pollution over China (Chen et al 2016;Chen et al 2019). Therefore, to make the DA system suitable for different emphasis and applications, a flexible aerosol assimilation capability is built within the WRFDA system in this study, which will facilitate developments and applications for more chemistry schemes in the future.…”

Section: Introductionmentioning

confidence: 99%

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Development and application of the WRFDA-Chem 3DVAR system: aiming to improve air quality forecast and diagnose model deficiencies

Sun

Liu

Chen

et al. 2020

Preprint

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Abstract. To improve the operational air quality forecasting over China, a new aerosol/gas phase pollutants assimilation capability is developed within the WRFDA system using 3DVAR algorithm. In this first application, the interface for MOSAIC aerosol scheme is built with flexible extending potentials. Based on the new WRFDA-Chem system, five experiments assimilating different surface observations, including PM2.5, PM10, SO2, NO2, O3, and CO are conducted for January 2017 along with a control experiment without DA. Results exhibit that the WRFDA-Chem system evidently improves the air quality forecasting. On the analysis aspect, the assimilation of surface observations reduces the bias and RMSE in the initial condition (IC) remarkably; on the forecast aspect, better forecast performances are acquired up to 24-h, in which the experiment assimilating the six pollutants simultaneously displays the best forecast skill overall. With respect to the impact of DA cycling frequency, the responses toward IC updating are found out to be different among the pollutants. For PM2.5, PM10, SO2 and CO, the forecast skills increase with the DA frequency; for O3, although improvements are acquired at the 6-h cycling frequency, the advantage of more frequent DA could be consumed by the disadvantage of unbalanced photochemistry (due to inaccurate precursor NOx/VOC ratios) from assimilating the existing observations (only O3 and NO2, but no VOC). Considering after one aspect (IC) in the model is corrected by DA, the deficiencies from other aspects (e.g., chemical reactions) could be more evident, this study further explores the model deficiencies by investigating the effects of assimilating gaseous precursors on the forecast of related aerosols. Results exhibit that the parameterization (uptake coefficients) in the newly added Sulfate-Nitrate-Ammonium (SNA) relevant heterogeneous reactions in the model are not fully appropriate although it best simulates observed SNA aerosols without DA; since the uptake coefficients were originally tuned under the inaccurate gaseous precursor scenarios without DA, the biases from the two aspects (SNA reactions and IC DA) were just compensated. In the future chemistry development, parameterizations (such as uptake coefficients) for different gaseous precursor scenarios should be adjusted and verified with the help of DA technique. According to these results, DA ameliorates certain aspects by using observation as constraints, and thus provides an opportunity to identify and diagnose the model deficiencies; it is useful especially when the uncertainties of various aspects are mixed up and the reaction paths are not clearly revealed. In the future, besides being used to improve the forecast through updating IC, DA could be treated as another approach to explore necessary developments in the model.

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Section: Model Description Observations and Methodologymentioning

confidence: 99%

Section: Wrf-chem Model and Emissionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Development and application of the WRFDA-Chem 3DVAR system: aiming to improve air quality forecast and diagnose model deficiencies

Sun

Liu

Chen

et al. 2020

Preprint

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“…Following Zheng et al (2015a) and Chen et al (2016), a parameterization scheme is adopted to simulate the aqueous phase production of nitrate (denoted as PM25_NO3):…”

Section: Wrf-chem-awac: New Aerosol Water Chemistry Module For Wrf-chemmentioning

confidence: 99%

“…Though the importance of reactions in aerosol water during severe haze has been widely accepted Zheng et al, 2015b;Chen et al, 2016;Cheng et al, 2016;Wang et al, 2016;Li et al, 2017a;Chen et al, 2019;Gen et al, 2019;Shao 20 et al, 2019;Wu et al, 2019;Xue et al, 2019), the exact formation pathway is still under debate. Except for the aforementioned reactions (i.e., reactions of NO2, O3, TMI and H2O2), heterogeneous production of hydroxymethanesulfonate (HMS) by SO2 and HCHO has also been proposed to contribute to the unexplained sulfate by models (Moch et al, 2018;Song et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Aerosol pH and chemical regimes of sulfate formation in aerosol water during winter haze in the North China Plain

Tao¹,

Su²,

Zheng³

et al. 2020

Preprint

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Abstract. Understanding the mechanism of haze formation is crucial for the development of deliberate pollution control strategies. Multiphase chemical reactions in aerosol water have been suggested as an important source of particulate sulfate during severe haze (Cheng et al., 2016; Wang et al., 2016). While the key role of aerosol water has been commonly accepted, the relative importance of different oxidation pathways in the aqueous phase is still under debate, mainly due to questions about aerosol pH. To investigate the spatio-temporal variability of aerosol pH and sulfate formation during winter in the North China Plain (NCP), we have developed a new aerosol water chemistry module (AWAC) for the WRF-Chem model (Weather Research and Forecasting model coupled with Chemistry). Using the WRF-Chem-AWAC model, we performed a comprehensive survey of the atmospheric conditions characteristic for wintertime in the NCP, focusing on January 2013. We find that aerosol pH exhibited a strong vertical gradient and distinct diurnal cycle, which was closely associated with the spatio-temporal variation in the relative abundance of acidic and alkaline fine particle components and their gaseous counterparts. Over Beijing, the average aerosol pH at the surface layer was ~ 5.4 and remained nearly constant around ~ 5 up to ~ 2 km above ground level; further aloft, the acidity rapidly increased to pH ~ 0 at ~ 3 km. The pattern of aerosol acidity increase with altitude persisted over the NCP, while the specific levels and gradients of pH varied between different regions. In the region north of ~ 41° N, the mean pH values at surface level were typically > 6 and the main pathway of sulfate formation in aerosol water was S(IV) oxidation by ozone. South of ~ 41° N, the mean pH values at surface level were typically in the range of 4.4 to 5.7, and different chemical regimes and reaction pathways of sulfate formation prevailed in four different regions, depending on reactant concentrations and atmospheric conditions. The NO2 reaction pathway prevailed in the megacity region of Beijing and the large area of Hebei Province to the south and west of Beijing, as well as part of Shandong Province. The transition metal ion (TMI) pathway dominated in the inland region to the west and the coastal regions to the east of Beijing, and the H2O2 pathway dominated in the region extending further south (Shandong and Henan Provinces). In all of these regions, the O3 and TMI pathways in aerosol water as well as the gas-particle partitioning of H2SO4 vapor became more important with increasing altitude. Although pH is sensitive to the abundance of NH3 and crustal particles, we show that the rapid production of sulfate in the NCP can be maintained over a wide range of aerosol acidity (e.g., pH = 4.2–5.7) with transitions from TMI pathway dominated to NO2/O3 pathway dominated regimes.

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Key Role of Nitrate in Phase Transitions of Urban Particles: Implications of Important Reactive Surfaces for Secondary Aerosol Formation

Sun

Liu

et al. 2018

JGR Atmospheres

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Ammonium sulfate (AS) and ammonium nitrate (AN) are key components of urban fine particles. Both field and model studies showed that heterogeneous reactions of SO2, NO2, and NH3 on wet aerosols accelerated the haze formation in northern China. However, little is known on phase transitions of AS‐AN containing haze particles. Here hygroscopic properties of laboratory‐generated AS‐AN particles and individual particles collected during haze events in an urban site were investigated using an individual particle hygroscopicity system. AS‐AN particles showed a two‐stage deliquescence at mutual deliquescence relative humidity (MDRH) and full deliquescence relative humidity (DRH) and three physical states: solid before MDRH, solid‐aqueous between MDRH and DRH, and aqueous after DRH. During hydration, urban haze particles displayed a solid core and aqueous shell at RH = 60–80% and aqueous phase at RH > 80%. Most particles were in aqueous phase at RH > 50% during dehydration. Our results show that AS content in individual particles determines their DRH and AN content determines their MDRH. AN content increase can reduce MDRH, which indicates occurrence of aqueous shell at lower RH. The humidity‐dependent phase transitions of nitrate‐abundant urban particles are important to provide reactive surfaces of secondary aerosol formation in the polluted air.

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Simulations of Sulfate-Nitrate-Ammonium (SNA) aerosols during the extreme haze events over Northern China in October 2014

Cited by 21 publications

References 19 publications

Development and application of the WRFDA-Chem 3DVAR system: aiming to improve air quality forecast and diagnose model deficiencies

Development and application of the WRFDA-Chem 3DVAR system: aiming to improve air quality forecast and diagnose model deficiencies

Aerosol pH and chemical regimes of sulfate formation in aerosol water during winter haze in the North China Plain

Key Role of Nitrate in Phase Transitions of Urban Particles: Implications of Important Reactive Surfaces for Secondary Aerosol Formation

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