Parameterization of sea-salt optical properties and physics of the associated radiative forcing
The optical properties of sea-salt aerosol have been parameterized at shortwave and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is teste...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2008-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/8/4787/2008/acp-8-4787-2008.pdf |
| _version_ | 1818067055302148096 |
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| author | J. Li X. Ma K. von Salzen S. Dobbie |
| author_facet | J. Li X. Ma K. von Salzen S. Dobbie |
| author_sort | J. Li |
| collection | DOAJ |
| description | The optical properties of sea-salt aerosol have been parameterized at shortwave and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is tested relative to Mie calculations and is found to be accurate to within a few percent. In the parameterization, the effects of the size distribution on the optical properties are accounted for in terms of effective radius of the sea-salt size distribution. This parameterization differs from previous works by being formulated directly with the wet sea-salt size distribution and, to our knowledge, this is the first published sea-salt parameterization to provide a parameterization for both shortwave and longwave wavelengths. <br><br> We have used this parameterization in a set of idealized 1-D radiative transfer calculations to investigate the sensitivity of various attributes of sea-salt forcing, including the dependency on sea-salt column loading, effective variance, solar angle, and surface albedo. From these sensitivity tests, it is found that sea-salt forcings for both shortwave and longwave spectra are linearly related to the sea-salt loading for realistic values of loadings. The radiative forcing results illustrate that the shortwave forcing is an order of magnitude greater than the longwave forcing results and opposite in sign, for various loadings. Forcing sensitivity studies show that the influence of effective variance for sea-salt is minor; therefore, only one value of effective variance is used in the parameterization. The dependence of sea-salt forcing with solar zenith angle illustrates an interesting result that sea-salt can generate a positive top-of-the-atmosphere result (i.e. warming) when the solar zenith angle is relatively small (i.e. <30&deg;). Finally, it is found that the surface albedo significantly affects the shortwave radiative forcing, with the forcing diminishing to zero as the surface albedo tends to unity. |
| first_indexed | 2024-12-10T15:17:36Z |
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| id | doaj.art-3ff2fa56e86942d5a6bc0a90b727829e |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-10T15:17:36Z |
| publishDate | 2008-08-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-3ff2fa56e86942d5a6bc0a90b727829e2022-12-22T01:43:46ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242008-08-0181647874798Parameterization of sea-salt optical properties and physics of the associated radiative forcingJ. LiX. MaK. von SalzenS. DobbieThe optical properties of sea-salt aerosol have been parameterized at shortwave and longwave wavelengths. The optical properties were parameterized in a simple functional form in terms of the ambient relative humidity based on Mie optical property calculations. The proposed parameterization is tested relative to Mie calculations and is found to be accurate to within a few percent. In the parameterization, the effects of the size distribution on the optical properties are accounted for in terms of effective radius of the sea-salt size distribution. This parameterization differs from previous works by being formulated directly with the wet sea-salt size distribution and, to our knowledge, this is the first published sea-salt parameterization to provide a parameterization for both shortwave and longwave wavelengths. <br><br> We have used this parameterization in a set of idealized 1-D radiative transfer calculations to investigate the sensitivity of various attributes of sea-salt forcing, including the dependency on sea-salt column loading, effective variance, solar angle, and surface albedo. From these sensitivity tests, it is found that sea-salt forcings for both shortwave and longwave spectra are linearly related to the sea-salt loading for realistic values of loadings. The radiative forcing results illustrate that the shortwave forcing is an order of magnitude greater than the longwave forcing results and opposite in sign, for various loadings. Forcing sensitivity studies show that the influence of effective variance for sea-salt is minor; therefore, only one value of effective variance is used in the parameterization. The dependence of sea-salt forcing with solar zenith angle illustrates an interesting result that sea-salt can generate a positive top-of-the-atmosphere result (i.e. warming) when the solar zenith angle is relatively small (i.e. <30&deg;). Finally, it is found that the surface albedo significantly affects the shortwave radiative forcing, with the forcing diminishing to zero as the surface albedo tends to unity.http://www.atmos-chem-phys.net/8/4787/2008/acp-8-4787-2008.pdf |
| spellingShingle | J. Li X. Ma K. von Salzen S. Dobbie Parameterization of sea-salt optical properties and physics of the associated radiative forcing Atmospheric Chemistry and Physics |
| title | Parameterization of sea-salt optical properties and physics of the associated radiative forcing |
| title_full | Parameterization of sea-salt optical properties and physics of the associated radiative forcing |
| title_fullStr | Parameterization of sea-salt optical properties and physics of the associated radiative forcing |
| title_full_unstemmed | Parameterization of sea-salt optical properties and physics of the associated radiative forcing |
| title_short | Parameterization of sea-salt optical properties and physics of the associated radiative forcing |
| title_sort | parameterization of sea salt optical properties and physics of the associated radiative forcing |
| url | http://www.atmos-chem-phys.net/8/4787/2008/acp-8-4787-2008.pdf |
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