| Autor: |
Hoffman, Alicia, Bertram, Timothy H., Holloway, Tracey, Harkey, Monica |
| Zdroj: |
Journal of Geophysical Research - Atmospheres; May 2024, Vol. 129 Issue: 10 |
| Abstrakt: |
Nitrogen oxides (NOx) have adverse human health impacts and play a central role in the production of ozone and PM2.5. Nighttime heterogeneous chemistry regulates the nocturnal reservoirs and sinks of NOxsuch as N2O5removal and ClNO2production. However, existing parameterizations of nocturnal NOxheterogeneous chemistry in air quality models do not capture the variability in observations. Here, we implemented for the first time in the Community Multiscale Air Quality (CMAQ) model the Gaston N2O5uptake (γ(N2O5)) mechanism that accounts for the role of particulate organic matter in regulating N2O5uptake and the Staudt ClNO2yield (Φ(ClNO2)) mechanism that includes the role of reactive solutes in suppressing ClNO2production. With the Gaston and Staudt parameterizations, the coarse mode contributed modestly to N2O5loss (17.2%) but significantly to ClNO2production (60.3%), highlighting the impact of coarse mode chemistry. The Gaston γ(N2O5) parameterization in the fine mode increased agreement between modeled N2O5concentration and observations (RMSEnew= 0.37ppb) compared to the model default (RMSEdefault= 0.43ppb). The Gaston γ(N2O5) parameterization was overall biased low due to underestimates in modeled particle oxygen to carbon ratio (O:C). The Staudt Φ(ClNO2) parameterization resulted in further underestimation (NMBnew= −73.7%) compared to the model default (NMBdefault= −37.9%) because of underestimation of fine mode particle chloride concentration. We expect that the updated parameterizations may more accurately capture the mean state and variability in γ(N2O5) and Φ(ClNO2) under conditions where model particulate O:C and chloride are better represented. Air pollutants such as nitrogen oxides (NOx) are regulated by the U.S. EPA because of their negative human health and environmental impacts. Modeling of NOxchemistry is important for both understanding what leads to air pollution events and assessing how to improve poor air quality. Accurate treatment of relevant nighttime reactions that impact NOxis necessary to reproduce air quality conditions, yet current model representations miss the effects of complex particle composition. We implement two updated mechanisms in the Community Multiscale Air Quality (CMAQ) model that are representative of complex particle chemistry with the goal of improving model predictions of nighttime NOx. The updated mechanisms improved performance of these nighttime reactions compared to existing model mechanisms for some chemical species, but none of the model simulations captured the full range of observed values. Further updates to the model representation of particle composition may result in additional improvements to nighttime NOxchemistry. Updated parameterizations for N2O5uptake and ClNO2yield in the Community Multiscale Air Quality (CMAQ) model highlight the impact of coarse mode chemistry on NOxThe Gaston N2O5uptake parameterization in the fine mode increased agreement between modeled and observed N2O5concentrationModel results show an underestimation of modeled particle oxygen to carbon ratio and fine mode particle chloride concentration Updated parameterizations for N2O5uptake and ClNO2yield in the Community Multiscale Air Quality (CMAQ) model highlight the impact of coarse mode chemistry on NOx The Gaston N2O5uptake parameterization in the fine mode increased agreement between modeled and observed N2O5concentration Model results show an underestimation of modeled particle oxygen to carbon ratio and fine mode particle chloride concentration |
| Databáze: |
Supplemental Index |
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