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| Titel |
Comment on "Reduced efficacy of marine cloud brightening geoengineering due to in-plume aerosol coagulation: parameterization and global implications" by Stuart et al. (2013) |
| VerfasserIn |
S. Anand, Y. S. Mayya |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 2 ; Nr. 15, no. 2 (2015-01-21), S.753-756 |
| Datensatznummer |
250119337
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| Publikation (Nr.) |
 copernicus.org/acp-15-753-2015.pdf |
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| Zusammenfassung |
| We examine the parameterized model of Stuart et al. (2013) vis-à-vis a diffusion-based
model proposed by us earlier (Anand and Mayya, 2011) to estimate the
fraction of aerosol particles surviving coagulation in a dispersing plume.
While the Stuart et al. approach is based on the solutions to the
coagulation problem in an expanding plume model, the diffusion-based
approach solves the diffusion–coagulation equation for a steady-state
standing plume to arrive at the survival fraction correlations. We discuss
the differences in the functional forms of the survival fraction expressions
obtained in the two approaches and compare the results for the case studies
presented in Stuart et al. (2013) involving different particle emission
rates and atmospheric stability categories. There appears to be a better
agreement between the two models at higher survival fractions as compared to
lower survival fractions; on the whole, the two models agree with each other
within a difference of 10%. The diffusion-based expression involves a
single exponent fit to a theoretically generated similarity variable
combining the parameters of the problem with inbuilt exponents and hence
avoids the multi-exponent parameterization exercise. It also possesses a
wider range of applicability in respect of the source and atmospheric
parameters as compared to that based on parameterization. However, in the
diffusion model, the choice of a representative value for the coagulation
coefficient is more prescriptive than rigorous, which has been addressed in
a more satisfactory manner by the parameterization method. The present
comparative exercise, although limited in scope, confirms the importance of
aerosol microphysical processes envisaged by Stuart et al. for cloud
brightening applications. In a larger context, it seems to suggest that
either of the two forms of expressions might be suitable for incorporation
into global-/regional-scale air pollution models for predicting the
contribution of localized sources to the particle number loading in the
atmosphere. |
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