Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events
Cloud and aerosol information is needed in trace gas retrievals from satellite measurements. The Fast REtrieval Scheme for Clouds from the Oxygen A band (FRESCO) cloud algorithm employs reflectance spectra of the O<sub>2</sub> A band around 760 nm to derive cloud pressure...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2012-10-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/12/9057/2012/acp-12-9057-2012.pdf |
| _version_ | 1818499888380379136 |
|---|---|
| author | P. Wang O. N. E. Tuinder L. G. Tilstra M. de Graaf P. Stammes |
| author_facet | P. Wang O. N. E. Tuinder L. G. Tilstra M. de Graaf P. Stammes |
| author_sort | P. Wang |
| collection | DOAJ |
| description | Cloud and aerosol information is needed in trace gas retrievals from satellite measurements. The Fast REtrieval Scheme for Clouds from the Oxygen A band (FRESCO) cloud algorithm employs reflectance spectra of the O<sub>2</sub> A band around 760 nm to derive cloud pressure and effective cloud fraction. In general, clouds contribute more to the O<sub>2</sub> A band reflectance than aerosols. Therefore, the FRESCO algorithm does not correct for aerosol effects in the retrievals and attributes the retrieved cloud information entirely to the presence of clouds, and not to aerosols. For events with high aerosol loading, aerosols may have a dominant effect, especially for almost cloud free scenes. We have analysed FRESCO cloud data and Absorbing Aerosol Index (AAI) data from the Global Ozone Monitoring Experiment (GOME-2) instrument on the Metop-A satellite for events with typical absorbing aerosol types, such as volcanic ash, desert dust and smoke. We find that the FRESCO effective cloud fractions are correlated with the AAI data for these absorbing aerosol events and that the FRESCO cloud pressure contains information on aerosol layer pressure. For cloud free scenes, the derived FRESCO cloud pressure is close to the aerosol layer pressure, especially for optically thick aerosol layers. For cloudy scenes, if the strongly absorbing aerosols are located above the clouds, then the retrieved FRESCO cloud pressure may represent the height of the aerosol layer rather than the height of the clouds. Combining FRESCO and AAI data, an estimate for the aerosol layer pressure can be given. |
| first_indexed | 2024-12-10T20:35:43Z |
| format | Article |
| id | doaj.art-d34905331c3a443783f4f6410cd79e7c |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-10T20:35:43Z |
| publishDate | 2012-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-d34905331c3a443783f4f6410cd79e7c2022-12-22T01:34:32ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242012-10-0112199057907710.5194/acp-12-9057-2012Interpretation of FRESCO cloud retrievals in case of absorbing aerosol eventsP. WangO. N. E. TuinderL. G. TilstraM. de GraafP. StammesCloud and aerosol information is needed in trace gas retrievals from satellite measurements. The Fast REtrieval Scheme for Clouds from the Oxygen A band (FRESCO) cloud algorithm employs reflectance spectra of the O<sub>2</sub> A band around 760 nm to derive cloud pressure and effective cloud fraction. In general, clouds contribute more to the O<sub>2</sub> A band reflectance than aerosols. Therefore, the FRESCO algorithm does not correct for aerosol effects in the retrievals and attributes the retrieved cloud information entirely to the presence of clouds, and not to aerosols. For events with high aerosol loading, aerosols may have a dominant effect, especially for almost cloud free scenes. We have analysed FRESCO cloud data and Absorbing Aerosol Index (AAI) data from the Global Ozone Monitoring Experiment (GOME-2) instrument on the Metop-A satellite for events with typical absorbing aerosol types, such as volcanic ash, desert dust and smoke. We find that the FRESCO effective cloud fractions are correlated with the AAI data for these absorbing aerosol events and that the FRESCO cloud pressure contains information on aerosol layer pressure. For cloud free scenes, the derived FRESCO cloud pressure is close to the aerosol layer pressure, especially for optically thick aerosol layers. For cloudy scenes, if the strongly absorbing aerosols are located above the clouds, then the retrieved FRESCO cloud pressure may represent the height of the aerosol layer rather than the height of the clouds. Combining FRESCO and AAI data, an estimate for the aerosol layer pressure can be given.http://www.atmos-chem-phys.net/12/9057/2012/acp-12-9057-2012.pdf |
| spellingShingle | P. Wang O. N. E. Tuinder L. G. Tilstra M. de Graaf P. Stammes Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events Atmospheric Chemistry and Physics |
| title | Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events |
| title_full | Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events |
| title_fullStr | Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events |
| title_full_unstemmed | Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events |
| title_short | Interpretation of FRESCO cloud retrievals in case of absorbing aerosol events |
| title_sort | interpretation of fresco cloud retrievals in case of absorbing aerosol events |
| url | http://www.atmos-chem-phys.net/12/9057/2012/acp-12-9057-2012.pdf |
| work_keys_str_mv | AT pwang interpretationoffrescocloudretrievalsincaseofabsorbingaerosolevents AT onetuinder interpretationoffrescocloudretrievalsincaseofabsorbingaerosolevents AT lgtilstra interpretationoffrescocloudretrievalsincaseofabsorbingaerosolevents AT mdegraaf interpretationoffrescocloudretrievalsincaseofabsorbingaerosolevents AT pstammes interpretationoffrescocloudretrievalsincaseofabsorbingaerosolevents |