Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMI
This study employed dual-azimuth scanning MAX-DOAS to monitor vertical column densities of NO<sub>2</sub> and HCHO in Shanghai during the summer and winter of 2023, and compared the results with Sentinel-5P TROPOMI data. Dual-azimuth scanning revealed a generally consistent trend in gas...
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2025-01-01
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| author | Hongmei Ren Ang Li Zhaokun Hu Nannan Shao Xinyan Yang Hairong Zhang Jiangman Xu Jinji Ma |
| author_facet | Hongmei Ren Ang Li Zhaokun Hu Nannan Shao Xinyan Yang Hairong Zhang Jiangman Xu Jinji Ma |
| author_sort | Hongmei Ren |
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| description | This study employed dual-azimuth scanning MAX-DOAS to monitor vertical column densities of NO<sub>2</sub> and HCHO in Shanghai during the summer and winter of 2023, and compared the results with Sentinel-5P TROPOMI data. Dual-azimuth scanning revealed a generally consistent trend in gas concentrations (r > 0.95), but concentrations at 90° were higher than those at 0°, especially near the surface. This suggests that averaging multiple azimuth angles is necessary to better represent regional pollution levels. During the observation period, diurnal patterns revealed that NO<sub>2</sub> exhibited a “double peak” in the morning and evening, which was more pronounced in the summer, while HCHO peaked between 13:00 and 15:00. Comparisons with the TROPOMI data demonstrated overall good agreement. However, the probability of TROPOMI’s NO<sub>2</sub> and HCHO measurements being lower than those of MAX-DOAS was 80% and 62.5%, respectively. Furthermore, TROPOMI tended to overestimate at high concentrations, with overestimation reaching 41.14% for NO<sub>2</sub> when exceeding 9.54 × 10<sup>15</sup> molecules/cm<sup>2</sup> and 25.93% for HCHO when exceeding 1.26 × 10<sup>16</sup> molecules/cm<sup>2</sup>. Sensitivity analysis of the sampling distance (0–40 km) between TROPOMI samples and the ground-based site, and the sampling time (±5 to ±60 min) relative to the TROPOMI overpass, revealed that using a sampling distance of 15–25 km for NO<sub>2</sub> and 10–20 km for HCHO, along with appropriately shortening sampling times in the winter and extending them in the summer, can effectively enhance the consistency between satellite and ground-based observations. These findings not only reveal the spatiotemporal distribution characteristics of regional pollutants but optimize the sampling time and distance parameters for satellite–ground observation validation, providing data support for improving and enhancing the accuracy of satellite retrieval algorithms. |
| format | Article |
| id | doaj-art-ece350a524b94ce6a14a2b47060608f9 |
| institution | DOAJ |
| issn | 2072-4292 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | MDPI AG |
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| series | Remote Sensing |
| spelling | doaj-art-ece350a524b94ce6a14a2b47060608f92025-08-20T02:48:03ZengMDPI AGRemote Sensing2072-42922025-01-0117335510.3390/rs17030355Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMIHongmei Ren0Ang Li1Zhaokun Hu2Nannan Shao3Xinyan Yang4Hairong Zhang5Jiangman Xu6Jinji Ma7School of Physics and Electronic Information, Anhui Normal University, Wuhu 241000, ChinaKey Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, ChinaKey Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, ChinaSchool of Physics and Electronic Information, Anhui Normal University, Wuhu 241000, ChinaSchool of Physics and Electronic Information, Anhui Normal University, Wuhu 241000, ChinaCixi Branch of Ningbo Municipal Bureau of Ecology and Environment, Cixi 315302, ChinaKey Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, ChinaSchool of Geography and Tourism, Anhui Normal University, Wuhu 241000, ChinaThis study employed dual-azimuth scanning MAX-DOAS to monitor vertical column densities of NO<sub>2</sub> and HCHO in Shanghai during the summer and winter of 2023, and compared the results with Sentinel-5P TROPOMI data. Dual-azimuth scanning revealed a generally consistent trend in gas concentrations (r > 0.95), but concentrations at 90° were higher than those at 0°, especially near the surface. This suggests that averaging multiple azimuth angles is necessary to better represent regional pollution levels. During the observation period, diurnal patterns revealed that NO<sub>2</sub> exhibited a “double peak” in the morning and evening, which was more pronounced in the summer, while HCHO peaked between 13:00 and 15:00. Comparisons with the TROPOMI data demonstrated overall good agreement. However, the probability of TROPOMI’s NO<sub>2</sub> and HCHO measurements being lower than those of MAX-DOAS was 80% and 62.5%, respectively. Furthermore, TROPOMI tended to overestimate at high concentrations, with overestimation reaching 41.14% for NO<sub>2</sub> when exceeding 9.54 × 10<sup>15</sup> molecules/cm<sup>2</sup> and 25.93% for HCHO when exceeding 1.26 × 10<sup>16</sup> molecules/cm<sup>2</sup>. Sensitivity analysis of the sampling distance (0–40 km) between TROPOMI samples and the ground-based site, and the sampling time (±5 to ±60 min) relative to the TROPOMI overpass, revealed that using a sampling distance of 15–25 km for NO<sub>2</sub> and 10–20 km for HCHO, along with appropriately shortening sampling times in the winter and extending them in the summer, can effectively enhance the consistency between satellite and ground-based observations. These findings not only reveal the spatiotemporal distribution characteristics of regional pollutants but optimize the sampling time and distance parameters for satellite–ground observation validation, providing data support for improving and enhancing the accuracy of satellite retrieval algorithms.https://www.mdpi.com/2072-4292/17/3/355nitrogen dioxide (NO<sub>2</sub>)formaldehyde (HCHO)MAX-DOASTROPOMIcomparative analysisShanghai |
| spellingShingle | Hongmei Ren Ang Li Zhaokun Hu Nannan Shao Xinyan Yang Hairong Zhang Jiangman Xu Jinji Ma Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMI Remote Sensing nitrogen dioxide (NO<sub>2</sub>) formaldehyde (HCHO) MAX-DOAS TROPOMI comparative analysis Shanghai |
| title | Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMI |
| title_full | Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMI |
| title_fullStr | Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMI |
| title_full_unstemmed | Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMI |
| title_short | Monitoring and Comparative Analysis of NO<sub>2</sub> and HCHO in Shanghai Using Dual-Azimuth Scanning MAX-DOAS and TROPOMI |
| title_sort | monitoring and comparative analysis of no sub 2 sub and hcho in shanghai using dual azimuth scanning max doas and tropomi |
| topic | nitrogen dioxide (NO<sub>2</sub>) formaldehyde (HCHO) MAX-DOAS TROPOMI comparative analysis Shanghai |
| url | https://www.mdpi.com/2072-4292/17/3/355 |
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