Sensitivity of cloud albedo to aerosol concentration and spectral dispersion of cloud droplet size distribution
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| Natura: | Artículo científico |
| Lingua: | en |
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Universidad Nacional Autónoma de México
2007
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| _version_ | 1876479631603793920 |
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| author | G. Iorga |
| author_facet | G. Iorga |
| contents | Sensitivity of cloud albedo to aerosol concentration and spectral dispersion of cloud droplet size distribution G. Iorga S. Stefan Biología cloud albedo effective radius spectral dispersion indirect aerosol effect Aerosol size distribution Both the enhancement of the aerosol number concentration and the relative dispersion of the cloud dropletsize distribution (spectral dispersion) on a regional scale can modify the cloud reflectivity. This work isfocused on the role that pre-cloud aerosol plays in cloud reflectivity. Log-normal aerosol size distributionswere used to describe two aerosol types: marine and rural. The number of aerosols that activate to dropletswas obtained based on Abdul-Razzak and Ghans (2000) activation parameterization. The cloud albedotaking into account the spectral dispersion effect in the parameterization of cloud effective radius and in thescattering asymmetry factor has been estimated. Two different scaling factors to account for dispersion wereused. The sensitivity of cloud albedo to spectral dispersion-cloud droplet number concentration relationshipin connection to the changes in liquid water content (LWC), and the cloud droplet effective radius has beenalso investigated. We obtained higher values of effective radius when dispersion is taken into account, withrespect to the base case (without considering dispersion). The inferred absolute differences in effective radiusvalues between calculations with each of the scaling factors are below 0.8 μm as LWC ranges between 0.1and 1.0 g m-3. The optical depth decreased by up to 14% (marine), and up to 29% (continental) when dispersionis considered in both effective radius and asymmetry factor (βLDR scaling factor). Correspondingly, therelative change in cloud albedo is up to 6% (marine) and up to 11% (continental) clouds. For continentalclouds, the calculated effective radius when dispersion is considered fits well within the measured range ofeffective radius in SCAR-B project. The calculated cloud albedo when dispersion is considered shows betteragreement with the estimated cloud albedo from measured effective radius in SCAR-B project than thecloud albedo calculated without dispersion. In cleaner conditions of marine clouds, only βPL-scaled albedofits satisfactory within the validity range of albedo inferred using an effective radius-liquid water contentrelationship proposed by Reid et al. (1999) from ASTEX project. The low correlation coefficient of the effectiveradius-liquid water content parameterization in ASTEX may also play a role within. 2007 artículo científico 0187-6236 https://www.redalyc.org/articulo.oa?id=56520302 en http://www.redalyc.org/revista.oa?id=565 Atmósfera application/pdf Universidad Nacional Autónoma de México Atmósfera (México) Num.3 Vol.20 |
| format | Artículo científico |
| id | redalyc_56520302 |
| institution | Redalyc |
| language | en |
| publishDate | 2007 |
| publisher | Universidad Nacional Autónoma de México |
| spellingShingle | Sensitivity of cloud albedo to aerosol concentration and spectral dispersion of cloud droplet size distribution G. Iorga Biología cloud albedo effective radius spectral dispersion indirect aerosol effect Aerosol size distribution Sensitivity of cloud albedo to aerosol concentration and spectral dispersion of cloud droplet size distribution G. Iorga S. Stefan Biología cloud albedo effective radius spectral dispersion indirect aerosol effect Aerosol size distribution Both the enhancement of the aerosol number concentration and the relative dispersion of the cloud dropletsize distribution (spectral dispersion) on a regional scale can modify the cloud reflectivity. This work isfocused on the role that pre-cloud aerosol plays in cloud reflectivity. Log-normal aerosol size distributionswere used to describe two aerosol types: marine and rural. The number of aerosols that activate to dropletswas obtained based on Abdul-Razzak and Ghans (2000) activation parameterization. The cloud albedotaking into account the spectral dispersion effect in the parameterization of cloud effective radius and in thescattering asymmetry factor has been estimated. Two different scaling factors to account for dispersion wereused. The sensitivity of cloud albedo to spectral dispersion-cloud droplet number concentration relationshipin connection to the changes in liquid water content (LWC), and the cloud droplet effective radius has beenalso investigated. We obtained higher values of effective radius when dispersion is taken into account, withrespect to the base case (without considering dispersion). The inferred absolute differences in effective radiusvalues between calculations with each of the scaling factors are below 0.8 μm as LWC ranges between 0.1and 1.0 g m-3. The optical depth decreased by up to 14% (marine), and up to 29% (continental) when dispersionis considered in both effective radius and asymmetry factor (βLDR scaling factor). Correspondingly, therelative change in cloud albedo is up to 6% (marine) and up to 11% (continental) clouds. For continentalclouds, the calculated effective radius when dispersion is considered fits well within the measured range ofeffective radius in SCAR-B project. The calculated cloud albedo when dispersion is considered shows betteragreement with the estimated cloud albedo from measured effective radius in SCAR-B project than thecloud albedo calculated without dispersion. In cleaner conditions of marine clouds, only βPL-scaled albedofits satisfactory within the validity range of albedo inferred using an effective radius-liquid water contentrelationship proposed by Reid et al. (1999) from ASTEX project. The low correlation coefficient of the effectiveradius-liquid water content parameterization in ASTEX may also play a role within. 2007 artículo científico 0187-6236 https://www.redalyc.org/articulo.oa?id=56520302 en http://www.redalyc.org/revista.oa?id=565 Atmósfera application/pdf Universidad Nacional Autónoma de México Atmósfera (México) Num.3 Vol.20 |
| title | Sensitivity of cloud albedo to aerosol concentration and spectral dispersion of cloud droplet size distribution |
| topic | Biología cloud albedo effective radius spectral dispersion indirect aerosol effect Aerosol size distribution |
| url | https://www.redalyc.org/articulo.oa?id=56520302 |