Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS
Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in a rural location of southwestern Ontario during the Border Air Quality and Meteorology Study. Slant column densities (SCDs) of NO<sub>2</sub> and O<sub>4</sub> were determined us...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2011-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/11/12475/2011/acp-11-12475-2011.pdf |
| _version_ | 1818027344046063616 |
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| author | M. O. Wenig D. Majonis A. Ng J. M. O'Brien K. L. Hayden S. Beirle J. R. Brook T. Wagner J. D. Halla R. McLaren |
| author_facet | M. O. Wenig D. Majonis A. Ng J. M. O'Brien K. L. Hayden S. Beirle J. R. Brook T. Wagner J. D. Halla R. McLaren |
| author_sort | M. O. Wenig |
| collection | DOAJ |
| description | Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in a rural location of southwestern Ontario during the Border Air Quality and Meteorology Study. Slant column densities (SCDs) of NO<sub>2</sub> and O<sub>4</sub> were determined using the standard DOAS technique. Using a radiative transfer model and the O<sub>4</sub> SCDs, aerosol optical depths were determined for clear sky conditions and compared to OMI, MODIS, AERONET, and local PM<sub>2.5</sub> measurements. This aerosol information was input to a radiative transfer model to calculate NO<sub>2</sub> air mass factors, which were fit to the measured NO<sub>2</sub> SCDs to determine tropospheric vertical column densities (VCDs) of NO<sub>2</sub>. The method of determining NO<sub>2</sub> VCDs in this way was validated for the first time by comparison to composite VCDs derived from aircraft and ground-based measurements of NO<sub>2</sub>. The new VCDs were compared to VCDs of NO<sub>2</sub> determined via retrievals from the satellite instruments SCIAMACHY and OMI, for overlapping time periods. The satellite-derived VCDs were higher, with a mean bias of +0.5–0.9×10<sup>15</sup> molec cm<sup>−2</sup>. This last finding is different from previous studies whereby MAX-DOAS geometric VCDs were higher than satellite determinations, albeit for urban areas with higher VCDs. An effective boundary layer height, BLH<sub>eff</sub>, is defined as the ratio of the tropospheric VCD and the ground level concentration of NO<sub>2</sub>. Variations of BLH<sub>eff</sub> can be linked to time of day, source region, stability of the atmosphere, and the presence or absence of elevated NO<sub>x</sub> sources. In particular, a case study is shown where a high VCD and BLH<sub>eff</sub> were observed when an elevated industrial plume of NO<sub>x</sub> and SO<sub>2</sub> was fumigated to the surface as a lake breeze impacted the measurement site. High BLH<sub>eff</sub> values (~1.9 km) were observed during a regional smog event when high winds from the SW and high convection promoted mixing throughout the boundary layer. During this event, the regional line flux of NO<sub>2</sub> through the region was estimated to be greater than 112 kg NO<sub>2</sub> km<sup>−1</sup> h<sup>−1</sup>. |
| first_indexed | 2024-12-10T04:46:24Z |
| format | Article |
| id | doaj.art-32b10bd4e20249d59261e7d3839bb111 |
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| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-10T04:46:24Z |
| publishDate | 2011-12-01 |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-32b10bd4e20249d59261e7d3839bb1112022-12-22T02:01:44ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242011-12-011123124751249810.5194/acp-11-12475-2011Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOASM. O. WenigD. MajonisA. NgJ. M. O'BrienK. L. HaydenS. BeirleJ. R. BrookT. WagnerJ. D. HallaR. McLarenMulti-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in a rural location of southwestern Ontario during the Border Air Quality and Meteorology Study. Slant column densities (SCDs) of NO<sub>2</sub> and O<sub>4</sub> were determined using the standard DOAS technique. Using a radiative transfer model and the O<sub>4</sub> SCDs, aerosol optical depths were determined for clear sky conditions and compared to OMI, MODIS, AERONET, and local PM<sub>2.5</sub> measurements. This aerosol information was input to a radiative transfer model to calculate NO<sub>2</sub> air mass factors, which were fit to the measured NO<sub>2</sub> SCDs to determine tropospheric vertical column densities (VCDs) of NO<sub>2</sub>. The method of determining NO<sub>2</sub> VCDs in this way was validated for the first time by comparison to composite VCDs derived from aircraft and ground-based measurements of NO<sub>2</sub>. The new VCDs were compared to VCDs of NO<sub>2</sub> determined via retrievals from the satellite instruments SCIAMACHY and OMI, for overlapping time periods. The satellite-derived VCDs were higher, with a mean bias of +0.5–0.9×10<sup>15</sup> molec cm<sup>−2</sup>. This last finding is different from previous studies whereby MAX-DOAS geometric VCDs were higher than satellite determinations, albeit for urban areas with higher VCDs. An effective boundary layer height, BLH<sub>eff</sub>, is defined as the ratio of the tropospheric VCD and the ground level concentration of NO<sub>2</sub>. Variations of BLH<sub>eff</sub> can be linked to time of day, source region, stability of the atmosphere, and the presence or absence of elevated NO<sub>x</sub> sources. In particular, a case study is shown where a high VCD and BLH<sub>eff</sub> were observed when an elevated industrial plume of NO<sub>x</sub> and SO<sub>2</sub> was fumigated to the surface as a lake breeze impacted the measurement site. High BLH<sub>eff</sub> values (~1.9 km) were observed during a regional smog event when high winds from the SW and high convection promoted mixing throughout the boundary layer. During this event, the regional line flux of NO<sub>2</sub> through the region was estimated to be greater than 112 kg NO<sub>2</sub> km<sup>−1</sup> h<sup>−1</sup>.http://www.atmos-chem-phys.net/11/12475/2011/acp-11-12475-2011.pdf |
| spellingShingle | M. O. Wenig D. Majonis A. Ng J. M. O'Brien K. L. Hayden S. Beirle J. R. Brook T. Wagner J. D. Halla R. McLaren Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS Atmospheric Chemistry and Physics |
| title | Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS |
| title_full | Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS |
| title_fullStr | Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS |
| title_full_unstemmed | Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS |
| title_short | Determination of tropospheric vertical columns of NO<sub>2</sub> and aerosol optical properties in a rural setting using MAX-DOAS |
| title_sort | determination of tropospheric vertical columns of no sub 2 sub and aerosol optical properties in a rural setting using max doas |
| url | http://www.atmos-chem-phys.net/11/12475/2011/acp-11-12475-2011.pdf |
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