Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016
<p>We use a state-of-the-art regional chemistry transport model (WRF-Chem v4.2.1) to simulate particulate air pollution over northern India during September–November 2016. This period includes a severe air pollution episode marked by exceedingly high levels of hourly PM<span class="inl...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/24/2239/2024/acp-24-2239-2024.pdf |
| _version_ | 1797300219775287296 |
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| author | P. Agarwal D. S. Stevenson M. R. Heal |
| author_facet | P. Agarwal D. S. Stevenson M. R. Heal |
| author_sort | P. Agarwal |
| collection | DOAJ |
| description | <p>We use a state-of-the-art regional chemistry transport model (WRF-Chem v4.2.1) to simulate particulate air pollution over northern India during September–November 2016. This period includes a severe air pollution episode marked by exceedingly high levels of hourly PM<span class="inline-formula"><sub>2.5</sub></span> (particulate matter having an aerodynamic diameter <span class="inline-formula">≤</span> 2.5 <span class="inline-formula">µ</span>m) during 30 October to 7 November, particularly over the wider Indo-Gangetic Plain (IGP). We provide a comprehensive evaluation of simulated seasonal meteorology (nudged by ERA5 reanalysis products) and aerosol chemistry (PM<span class="inline-formula"><sub>2.5</sub></span> and its black carbon (BC) component) using a range of ground-based, satellite and reanalysis products, with a focus on the November 2016 haze episode. We find the daily and diurnal features in simulated surface temperature show the best agreement followed by relative humidity, with the largest discrepancies being an overestimate of night-time wind speeds (up to 1.5 m s<span class="inline-formula"><sup>−1</sup></span>) confirmed by both ground and radiosonde observations. Upper-air meteorology comparisons with radiosonde observations show excellent model skill in reproducing the vertical temperature gradient (<span class="inline-formula"><i>r</i>>0.9</span>). We evaluate modelled PM<span class="inline-formula"><sub>2.5</sub></span> at 20 observation sites across the IGP including eight in Delhi and compare simulated aerosol optical depth (AOD) with data from four AERONET sites. We also compare our model aerosol results with MERRA-2 reanalysis aerosol fields and MODIS satellite AOD. We find that the model captures many features of the observed aerosol distributions but tends to overestimate PM<span class="inline-formula"><sub>2.5</sub></span> during September (by a factor of 2) due to too much dust, and underestimate peak PM<span class="inline-formula"><sub>2.5</sub></span> during the severe episode. Delhi experiences some of the highest daily mean PM<span class="inline-formula"><sub>2.5</sub></span> concentrations within the study region, with dominant components nitrate (<span class="inline-formula">∼25</span> %), dust (<span class="inline-formula">∼25</span> %), secondary organic aerosols (<span class="inline-formula">∼20</span> %) and ammonium (<span class="inline-formula">∼10</span> %). Modelled PM<span class="inline-formula"><sub>2.5</sub></span> and BC spatially correlate well with MERRA-2 products across the whole domain. High AOD at 550nm across the IGP is also well predicted by the model relative to MODIS satellite (<span class="inline-formula"><i>r</i>≥0.8</span>) and ground-based AERONET observations (<span class="inline-formula"><i>r</i>≥0.7</span>), except during September. Overall, the model realistically captures the seasonal and spatial variations of meteorology and ambient pollution over northern India. However, the observed underestimations in pollutant concentrations likely come from a combination of underestimated emissions, too much night-time dispersion, and some missing or poorly represented aerosol chemistry processes. Nevertheless, we find the model is sufficiently accurate to be a useful tool for exploring the sources and processes that control PM<span class="inline-formula"><sub>2.5</sub></span> levels during severe pollution episodes.</p> |
| first_indexed | 2024-03-07T23:04:09Z |
| format | Article |
| id | doaj.art-652235c2638745b3aeb4dea1c7814913 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-03-07T23:04:09Z |
| publishDate | 2024-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-652235c2638745b3aeb4dea1c78149132024-02-22T07:31:12ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242024-02-01242239226610.5194/acp-24-2239-2024Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016P. Agarwal0D. S. Stevenson1M. R. Heal2School of GeoSciences, University of Edinburgh, Crew Building, Edinburgh, EH9 3FF, UKSchool of GeoSciences, University of Edinburgh, Crew Building, Edinburgh, EH9 3FF, UKSchool of Chemistry, University of Edinburgh, Joseph Black Building, Edinburgh, EH9 3FJ, UK<p>We use a state-of-the-art regional chemistry transport model (WRF-Chem v4.2.1) to simulate particulate air pollution over northern India during September–November 2016. This period includes a severe air pollution episode marked by exceedingly high levels of hourly PM<span class="inline-formula"><sub>2.5</sub></span> (particulate matter having an aerodynamic diameter <span class="inline-formula">≤</span> 2.5 <span class="inline-formula">µ</span>m) during 30 October to 7 November, particularly over the wider Indo-Gangetic Plain (IGP). We provide a comprehensive evaluation of simulated seasonal meteorology (nudged by ERA5 reanalysis products) and aerosol chemistry (PM<span class="inline-formula"><sub>2.5</sub></span> and its black carbon (BC) component) using a range of ground-based, satellite and reanalysis products, with a focus on the November 2016 haze episode. We find the daily and diurnal features in simulated surface temperature show the best agreement followed by relative humidity, with the largest discrepancies being an overestimate of night-time wind speeds (up to 1.5 m s<span class="inline-formula"><sup>−1</sup></span>) confirmed by both ground and radiosonde observations. Upper-air meteorology comparisons with radiosonde observations show excellent model skill in reproducing the vertical temperature gradient (<span class="inline-formula"><i>r</i>>0.9</span>). We evaluate modelled PM<span class="inline-formula"><sub>2.5</sub></span> at 20 observation sites across the IGP including eight in Delhi and compare simulated aerosol optical depth (AOD) with data from four AERONET sites. We also compare our model aerosol results with MERRA-2 reanalysis aerosol fields and MODIS satellite AOD. We find that the model captures many features of the observed aerosol distributions but tends to overestimate PM<span class="inline-formula"><sub>2.5</sub></span> during September (by a factor of 2) due to too much dust, and underestimate peak PM<span class="inline-formula"><sub>2.5</sub></span> during the severe episode. Delhi experiences some of the highest daily mean PM<span class="inline-formula"><sub>2.5</sub></span> concentrations within the study region, with dominant components nitrate (<span class="inline-formula">∼25</span> %), dust (<span class="inline-formula">∼25</span> %), secondary organic aerosols (<span class="inline-formula">∼20</span> %) and ammonium (<span class="inline-formula">∼10</span> %). Modelled PM<span class="inline-formula"><sub>2.5</sub></span> and BC spatially correlate well with MERRA-2 products across the whole domain. High AOD at 550nm across the IGP is also well predicted by the model relative to MODIS satellite (<span class="inline-formula"><i>r</i>≥0.8</span>) and ground-based AERONET observations (<span class="inline-formula"><i>r</i>≥0.7</span>), except during September. Overall, the model realistically captures the seasonal and spatial variations of meteorology and ambient pollution over northern India. However, the observed underestimations in pollutant concentrations likely come from a combination of underestimated emissions, too much night-time dispersion, and some missing or poorly represented aerosol chemistry processes. Nevertheless, we find the model is sufficiently accurate to be a useful tool for exploring the sources and processes that control PM<span class="inline-formula"><sub>2.5</sub></span> levels during severe pollution episodes.</p>https://acp.copernicus.org/articles/24/2239/2024/acp-24-2239-2024.pdf |
| spellingShingle | P. Agarwal D. S. Stevenson M. R. Heal Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016 Atmospheric Chemistry and Physics |
| title | Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016 |
| title_full | Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016 |
| title_fullStr | Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016 |
| title_full_unstemmed | Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016 |
| title_short | Evaluation of WRF-Chem-simulated meteorology and aerosols over northern India during the severe pollution episode of 2016 |
| title_sort | evaluation of wrf chem simulated meteorology and aerosols over northern india during the severe pollution episode of 2016 |
| url | https://acp.copernicus.org/articles/24/2239/2024/acp-24-2239-2024.pdf |
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