How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponent
<p>Satellite-based aerosol optical depth (AOD) has gained popularity as a powerful data source for calibrating aerosol models and correcting model errors through data assimilation. However, simulated airborne particle mass concentrations are not directly comparable to satellite-based AODs. For...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-01-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/1641/2023/acp-23-1641-2023.pdf |
| _version_ | 1828052904247820288 |
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| author | J. Jin J. Jin B. Henzing A. Segers |
| author_facet | J. Jin J. Jin B. Henzing A. Segers |
| author_sort | J. Jin |
| collection | DOAJ |
| description | <p>Satellite-based aerosol optical depth (AOD) has gained popularity as a powerful data source for calibrating aerosol models and correcting model errors through data assimilation. However, simulated airborne particle mass concentrations are not directly comparable to satellite-based AODs. For this, an AOD operator needs to be developed that can convert the simulated mass concentrations into model AODs. The AOD operator is most sensitive to the input of the particle size and chemical composition of aerosols. Furthermore, assumptions regarding particle size vary significantly amongst model AOD operators. More importantly, satellite retrieval algorithms rely on different size assumptions. Consequently, the differences between the simulations and observations do not always reflect the actual difference in aerosol amount.</p>
<p>In this study, the sensitivity of the AOD operator to aerosol properties has been explored. We conclude that, to avoid inconsistencies between the AOD operator and retrieved properties, a common understanding of the particle size is required. Accordingly, we designed a hybrid assimilation methodology (<i>hybrid</i> AOD assimilation) that includes two sequentially conducted procedures. First, aerosol size in the model operator has
been brought closer to the assumption of the satellite retrieval algorithm via assimilation of Ångström exponents. This ensures that the model AOD operator is more consistent with the AOD retrieval. The second step in the methodology concerns optimization of aerosol mass concentrations through direct assimilation of AOD (<i>standard</i> AOD
assimilation). The hybrid assimilation method is tested over the European domain using Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue products. The corrections made to the model aerosol size information are validated through a comparison with the ground-based Aerosol Robotic Network (AERONET) optical product. The increments in surface aerosol mass concentration that occur due to either the standard AOD
assimilation analysis or the hybrid AOD assimilation analysis are evaluated against independent ground PM<span class="inline-formula"><sub>2.5</sub></span> observations.
The standard analysis always results in relatively accurate posterior AOD distributions; however, the corrections are hardly transferred into better aerosol mass concentrations due to the uncertainty in the AOD operator. In contrast, the model AOD and mass concentration states are considerably more accurate when using the hybrid methodology.</p> |
| first_indexed | 2024-04-10T19:59:06Z |
| format | Article |
| id | doaj.art-41b1612c647a4016a692112cccbc8e21 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-10T19:59:06Z |
| publishDate | 2023-01-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-41b1612c647a4016a692112cccbc8e212023-01-27T10:42:11ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242023-01-01231641166010.5194/acp-23-1641-2023How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponentJ. Jin0J. Jin1B. Henzing2A. Segers3Department of Climate, Air and Sustainability, TNO, Utrecht, the Netherlandsnow at: Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing, Jiangsu, ChinaDepartment of Climate, Air and Sustainability, TNO, Utrecht, the NetherlandsDepartment of Climate, Air and Sustainability, TNO, Utrecht, the Netherlands<p>Satellite-based aerosol optical depth (AOD) has gained popularity as a powerful data source for calibrating aerosol models and correcting model errors through data assimilation. However, simulated airborne particle mass concentrations are not directly comparable to satellite-based AODs. For this, an AOD operator needs to be developed that can convert the simulated mass concentrations into model AODs. The AOD operator is most sensitive to the input of the particle size and chemical composition of aerosols. Furthermore, assumptions regarding particle size vary significantly amongst model AOD operators. More importantly, satellite retrieval algorithms rely on different size assumptions. Consequently, the differences between the simulations and observations do not always reflect the actual difference in aerosol amount.</p> <p>In this study, the sensitivity of the AOD operator to aerosol properties has been explored. We conclude that, to avoid inconsistencies between the AOD operator and retrieved properties, a common understanding of the particle size is required. Accordingly, we designed a hybrid assimilation methodology (<i>hybrid</i> AOD assimilation) that includes two sequentially conducted procedures. First, aerosol size in the model operator has been brought closer to the assumption of the satellite retrieval algorithm via assimilation of Ångström exponents. This ensures that the model AOD operator is more consistent with the AOD retrieval. The second step in the methodology concerns optimization of aerosol mass concentrations through direct assimilation of AOD (<i>standard</i> AOD assimilation). The hybrid assimilation method is tested over the European domain using Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue products. The corrections made to the model aerosol size information are validated through a comparison with the ground-based Aerosol Robotic Network (AERONET) optical product. The increments in surface aerosol mass concentration that occur due to either the standard AOD assimilation analysis or the hybrid AOD assimilation analysis are evaluated against independent ground PM<span class="inline-formula"><sub>2.5</sub></span> observations. The standard analysis always results in relatively accurate posterior AOD distributions; however, the corrections are hardly transferred into better aerosol mass concentrations due to the uncertainty in the AOD operator. In contrast, the model AOD and mass concentration states are considerably more accurate when using the hybrid methodology.</p>https://acp.copernicus.org/articles/23/1641/2023/acp-23-1641-2023.pdf |
| spellingShingle | J. Jin J. Jin B. Henzing A. Segers How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponent Atmospheric Chemistry and Physics |
| title | How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponent |
| title_full | How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponent |
| title_fullStr | How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponent |
| title_full_unstemmed | How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponent |
| title_short | How aerosol size matters in aerosol optical depth (AOD) assimilation and the optimization using the Ångström exponent |
| title_sort | how aerosol size matters in aerosol optical depth aod assimilation and the optimization using the angstrom exponent |
| url | https://acp.copernicus.org/articles/23/1641/2023/acp-23-1641-2023.pdf |
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