On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors
The accurate determination of nitrogen dioxide (NO<sub>2</sub>) tropospheric vertical columns from satellite measurements depends strongly on the airmass factor (AMF) used. A sensitivity study was performed with the radiative transfer model SCIATRAN to better understand the impact of aer...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2010-04-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/3/475/2010/amt-3-475-2010.pdf |
| _version_ | 1818826961550573568 |
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| author | M. Beekmann Q. J. Zhang A. Kokhanovsky A. Richter M. Vrekoussis J. Leitão J. P. Burrows |
| author_facet | M. Beekmann Q. J. Zhang A. Kokhanovsky A. Richter M. Vrekoussis J. Leitão J. P. Burrows |
| author_sort | M. Beekmann |
| collection | DOAJ |
| description | The accurate determination of nitrogen dioxide (NO<sub>2</sub>) tropospheric vertical columns from satellite measurements depends strongly on the airmass factor (AMF) used. A sensitivity study was performed with the radiative transfer model SCIATRAN to better understand the impact of aerosols on the calculation of NO<sub>2</sub> AMFs. This influence was studied by varying the NO<sub>2</sub> and aerosol vertical distributions, as well as physical and optical properties of the particles. In terms of aerosol definitions, the key factors for these calculations were identified as the relation between trace gas and aerosol vertical profiles, the optical depth of the aerosol layer, and single scattering albedo. In addition, surface albedo also has a large impact on the calculations. Overall it was found that particles mixed with the trace gas increases the measurements' sensitivity, but only when the aerosol is not very absorbing. The largest change, a factor of ~2 relative to the situation without aerosols, was found when a low layer of aerosol (600 m) was combined with a homogenous NO<sub>2</sub> layer of 1.0 km. A layer of aerosol above the NO<sub>2</sub> usually reduces the sensitivity of the satellite measurement. This situation is found mostly for runs with discrete elevated aerosol layers (representative for long-range transport) that can generate a decrease of the AMF values of up to 70%. The use of measured aerosol profiles and modelled NO<sub>2</sub> resulted, generally, in much smaller changes of AMF relative to the pure Rayleigh case. Exceptions are some events of elevated layers with high aerosol optical depth that lead to a strong decrease of the AMF values. These results highlight the importance of aerosols in the retrieval of tropospheric NO<sub>2</sub> columns from space and indicate the need for detailed information on aerosol properties and vertical distribution. |
| first_indexed | 2024-12-19T00:35:59Z |
| format | Article |
| id | doaj.art-d85aa72effe14a2685094bf9626bb076 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-19T00:35:59Z |
| publishDate | 2010-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-d85aa72effe14a2685094bf9626bb0762022-12-21T20:44:49ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482010-04-013247549310.5194/amt-3-475-2010On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factorsM. BeekmannQ. J. ZhangA. KokhanovskyA. RichterM. VrekoussisJ. LeitãoJ. P. BurrowsThe accurate determination of nitrogen dioxide (NO<sub>2</sub>) tropospheric vertical columns from satellite measurements depends strongly on the airmass factor (AMF) used. A sensitivity study was performed with the radiative transfer model SCIATRAN to better understand the impact of aerosols on the calculation of NO<sub>2</sub> AMFs. This influence was studied by varying the NO<sub>2</sub> and aerosol vertical distributions, as well as physical and optical properties of the particles. In terms of aerosol definitions, the key factors for these calculations were identified as the relation between trace gas and aerosol vertical profiles, the optical depth of the aerosol layer, and single scattering albedo. In addition, surface albedo also has a large impact on the calculations. Overall it was found that particles mixed with the trace gas increases the measurements' sensitivity, but only when the aerosol is not very absorbing. The largest change, a factor of ~2 relative to the situation without aerosols, was found when a low layer of aerosol (600 m) was combined with a homogenous NO<sub>2</sub> layer of 1.0 km. A layer of aerosol above the NO<sub>2</sub> usually reduces the sensitivity of the satellite measurement. This situation is found mostly for runs with discrete elevated aerosol layers (representative for long-range transport) that can generate a decrease of the AMF values of up to 70%. The use of measured aerosol profiles and modelled NO<sub>2</sub> resulted, generally, in much smaller changes of AMF relative to the pure Rayleigh case. Exceptions are some events of elevated layers with high aerosol optical depth that lead to a strong decrease of the AMF values. These results highlight the importance of aerosols in the retrieval of tropospheric NO<sub>2</sub> columns from space and indicate the need for detailed information on aerosol properties and vertical distribution.http://www.atmos-meas-tech.net/3/475/2010/amt-3-475-2010.pdf |
| spellingShingle | M. Beekmann Q. J. Zhang A. Kokhanovsky A. Richter M. Vrekoussis J. Leitão J. P. Burrows On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors Atmospheric Measurement Techniques |
| title | On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors |
| title_full | On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors |
| title_fullStr | On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors |
| title_full_unstemmed | On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors |
| title_short | On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors |
| title_sort | on the improvement of no sub 2 sub satellite retrievals aerosol impact on the airmass factors |
| url | http://www.atmos-meas-tech.net/3/475/2010/amt-3-475-2010.pdf |
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