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Emission inventories (EIs) are vital for air quality modeling. Specific research goals often require modifying EIs from diverse data sources, demanding significant code development. In this study, we utilized and further developed the High Elective Resolution Modeling Emission System version three for Global and Regional domains (HERMESv3_gr). This user-friendly processing system was adapted for generating EIs compatible with the Chemistry Transport Model Tracel Model 5 Massive Parallel (TM5-MP). The results indicate that HERMESv3_gr is capable of generating EIs with negligible biases ( 10 − 7 relative differences) for TM5-MP, showcasing its effectiveness. We applied HERMESv3_gr to integrate the EI Regional Emission inventory in Asia (REAS) into the global EI Community Emission Data System (CEDS). Comparison of model results using CEDS alone and the integrated EI against measurement data for various pollutants globally revealed small improvements for carbon monoxide (1%) ethane (1–2%), and nitrogen oxide (2%) and larger for propane (5–7%). Ozone in the northern hemisphere improved by about 2% while in the southern hemisphere improvements of 5% could be observed. Our findings highlight the importance of carefully considering the effects of EI integration for accurate air quality modeling. [ABSTRACT FROM AUTHOR]

The Atmospheric Oxidation Capacity (AOC), often referred to as the self-cleansing ability of the atmosphere, considerably affects the concentrations of photochemical air pollutants. Despite substantial reductions in anthropogenic emissions of key chemical compounds in China, the mechanisms that determine the changes in the atmospheric oxidation capacity are still not sufficiently understood. Here, a regional chemical transport model is employed to quantify the sensitivity of air pollutants and photochemical parameters to specified emission reductions in China for conditions of January and July 2018 as representative. The model simulations show that, in winter, a 50 % decrease in nitrogen oxides (NOx) emissions leads to an 8–10 ppbv (15–20 %) increase in surface ozone concentrations across China. In summer, the ozone concentration decreases by 2–8 ppbv (3–12 %) in NOx-limited areas, while ozone increases by up to 12 ppbv (15 %) in volatile organic compounds (VOCs)-limited areas. This ozone increase is associated with a reduced NOx-titration effect and higher levels of hydroperoxyl (HO2) radical due to decreased aerosol uptake. With an additional 50 % reduction in anthropogenic VOCs emission, the predicted ozone concentration decreases by 5–12 ppbv (6–15 %) in the entire geographic area of China, with an exception in the areas, where the role of BVOCs is crucial to ozone formation. Further, the adopted reduction in NOx emission leads to an increase of AOC by 18 % in VOC-limited areas. This specific increase is associated with the combined effect of enhanced radical cycles associated with the photolysis of oxidized VOCs (OVOCs) and the oxidation of alkenes by hydroxyl (OH) radical and O3. A large reduction of daytime AOC in summer results from the reduction in anthropogenic VOCs emission, with a dominant contribution from the reaction of OH radical with reduced alkenes, followed by the reactions with depleted aromatics and OVOCs. This study highlights that photolysis of OVOCs and oxidation of alkenes in urban areas when NOx emission is reduced leads to an increase in O3. To mitigate ozone rises in urban areas, a joint reduction in the emission of NOx and specific VOCs species, including alkenes and aromatics and photodegradable OVOCs, should be implemented. [ABSTRACT FROM AUTHOR]

Atmospheric oxidation capacity (AOC) characterizes the ability of the atmosphere to scavenge air pollutants. However, the processes involved in China, where anthropogenic emissions have changed dramatically in the past decade, are not fully understood. A detailed analysis of different parameters that determine the AOC in China is presented on the basis of numerical simulations performed with the regional chemical–meteorological Weather Research and Forecasting model with Chemistry (WRF-Chem). The model shows that the aerosol effects related to extinction and heterogeneous processes produce a decrease in surface ozone of approximately 8–10 ppbv in NO x -limited rural areas and an increase of 5–10 ppbv in VOC-limited urban areas. In this latter case, the ozone increase is noticeable for aerosol concentrations ranging from 20 to 45 µ g m -3 in July 2018. The ozone reduction in NO x -sensitive regions is due to the combined effect of nitrogen dioxide and peroxy radical uptake on particles and of the light extinction by aerosols, which affects the photodissociation rates. The ozone increase in VOC-sensitive areas is attributed to the uptake of NO 2 by aerosols, which is offset by the reduced ozone formation associated with HO 2 uptake and with aerosol extinction. Our study concludes that more than 90 % of the daytime AOC is due to the reaction of the hydroxyl radical with VOCs and carbon monoxide. In urban areas, during summertime, the main contributions to daytime AOC are the reactions of OH with alkene (30 %–50 %), oxidized volatile organic compounds (OVOCs) (33 %–45 %), and carbon monoxide (20 %–45 %). In rural areas, the largest contribution results from the reaction of OH with alkenes (60 %). Nocturnal AOC is dominantly attributed to the reactions with the nitrate radical (50 %–70 %). Our results shed light on the contribution of aerosol-related NO x loss and the high reactivity of alkenes for photochemical pollution. With the reduction in aerosols and anthropogenic ozone precursors, the chemistry of nitrogen and temperature-sensitive VOCs will become increasingly important. More attention needs to be paid to the role of photodegradable OVOCs and nocturnal oxidants in the formation of secondary pollutants. [ABSTRACT FROM AUTHOR]

Ice-nucleating particles (INPs) enable ice formation, profoundly affecting the microphysical and radiative properties, lifetimes, and precipitation rates of clouds. Mineral dust emitted from arid regions, particularly potassium-containing feldspar (K-feldspar), has been shown to be a very effective INP through immersion freezing in mixed-phase clouds. However, despite the fact that quartz has a significantly lower ice nucleation activity, it is more abundant than K-feldspar in atmospheric desert dust and therefore may be a significant source of INPs. In this contribution, we test this hypothesis by investigating the global and regional importance of quartz as a contributor to INPs in the atmosphere relative to K-feldspar. We have extended a global 3-D chemistry transport model (TM4-ECPL) to predict INP concentrations from both K-feldspar and quartz mineral dust particles with state-of-the-art parameterizations using the ice-active surface-site approach for immersion freezing. Our results show that, although K-feldspar remains the most important contributor to INP concentrations globally, affecting mid-level mixed-phase clouds, the contribution of quartz can also be significant. Quartz dominates the lowest and the highest altitudes of dust-derived INPs, affecting mainly low-level and high-level mixed-phase clouds. The consideration of quartz INPs also improves the comparison between simulations and observations at low temperatures. Our simulated INP concentrations predict ∼ 51 % of the observations gathered from different campaigns within 1 order of magnitude and ∼ 69 % within 1.5 orders of magnitude, despite the omission of other potentially important INP aerosol precursors like marine bioaerosols. Our findings support the inclusion of quartz in addition to K-feldspar as an INP in climate models and highlight the need for further constraining their abundance in arid soil surfaces along with their abundance, size distribution, and mixing state in the emitted dust atmospheric particles. [ABSTRACT FROM AUTHOR]

This work documents and evaluates the tropospheric gas-phase chemical mechanism MOGUNTIA in the three-dimensional chemistry transport model TM5-MP. Compared to the modified CB05 (mCB05) chemical mechanism previously used in the model, MOGUNTIA includes a detailed representation of the light hydrocarbons (C1–C4) and isoprene, along with a simplified chemistry representation of terpenes and aromatics. Another feature implemented in TM5-MP for this work is the use of the Rosenbrock solver in the chemistry code, which can replace the classical Euler backward integration method of the model. Global budgets of ozone (O3), carbon monoxide (CO), hydroxyl radicals (OH), nitrogen oxides (NOx), and volatile organic compounds (VOCs) are analyzed, and their mixing ratios are compared with a series of surface, aircraft, and satellite observations for the year 2006. Both mechanisms appear to be able to satisfactorily represent observed mixing ratios of important trace gases, with the MOGUNTIA chemistry configuration yielding lower biases than mCB05 compared to measurements in most of the cases. However, the two chemical mechanisms fail to reproduce the observed mixing ratios of light VOCs, indicating insufficient primary emission source strengths, oxidation that is too fast, and/or a low bias in the secondary contribution to C2–C3 organics via VOC atmospheric oxidation. Relative computational memory and time requirements of the different model configurations are also compared and discussed. Overall, the MOGUNTIA scheme simulates a large suite of oxygenated VOCs that are observed in the atmosphere at significant levels. This significantly expands the possible applications of TM5-MP. [ABSTRACT FROM AUTHOR]