Cloud albedo changes in response to anthropogenic sulfate and non-sulfate aerosol forcings in CMIP5 models
The effects of different aerosol types on cloud albedo are analysed using the linear relation between total albedo and cloud fraction found on a monthly mean scale in regions of subtropical marine stratocumulus clouds and the influence of simulated aerosol variations on this relation. Model exper...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-07-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/9145/2017/acp-17-9145-2017.pdf |
| Summary: | The effects of different aerosol types on cloud albedo are analysed using the
linear relation between total albedo and cloud fraction found on a monthly
mean scale in regions of subtropical marine stratocumulus clouds and the
influence of simulated aerosol variations on this relation. Model experiments
from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to
separately study the responses to increases in sulfate, non-sulfate and all
anthropogenic aerosols. A cloud brightening on the month-to-month scale due
to variability in the background aerosol is found to dominate even in the
cases where anthropogenic aerosols are added. The aerosol composition is of
importance for this cloud brightening, that is thereby region dependent.
There is indication that absorbing aerosols to some extent counteract the
cloud brightening but scene darkening with increasing aerosol burden is
generally not supported, even in regions where absorbing aerosols dominate.
Month-to-month cloud albedo variability also confirms the importance of
liquid water content for cloud albedo. Regional, monthly mean cloud albedo is
found to increase with the addition of anthropogenic aerosols and more so
with sulfate than non-sulfate. Changes in cloud albedo between experiments
are related to changes in cloud water content as well as droplet size
distribution changes, so that models with large increases in liquid water
path and/or cloud droplet number show large cloud albedo increases with
increasing aerosol. However, no clear relation between model sensitivities to
aerosol variations on the month-to-month scale and changes in cloud albedo
due to changed aerosol burden is found. |
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| ISSN: | 1680-7316 1680-7324 |