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| Titel |
Impact of aerosols on marine cloud microphysics over the Indian Ocean using satellite data. |
| VerfasserIn |
Sofiya Rao, Sagnik Dey |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138053
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| Publikation (Nr.) |
 EGU/EGU2017-960.pdf |
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| Zusammenfassung |
| Aerosol-cloud interaction is the one of the least understood and largest sources of uncertainty
in quantifying climate forcing. Despite progress, the problem remains unresolved because of
the buffering effect of meteorology and therefore it is suggested to separate the
meteorological forcing from aerosol forcing focusing on different cloud types (Stevens and
Feingold 2009). However, most of the previous studies on aerosol-cloud interaction over the
Indian Ocean (including INDOEX) are limited to either one particular season or short period.
We examine relationships between aerosol and cloud parameters using MODIS
data sets for 15 years (2000-2015) period over Indian Ocean. We separated the
meteorological forcing from aerosol forcing. In both the Arabian Sea (AS) and Bay
of Bengal (BOB), the meteorological forcing is largest in the monsoon. In all the
four seasons, cloud microphysical properties are more sensitive to aerosol optical
depth (AOD) over the AS compared to BOB. Further analysis reveals presence of
semi-direct effect in the winter season. Influence of aerosols on liquid water path
(LWP) – cloud effective radius (Reff) relation is quantified. Cloud albedo (Rc)
dependency on LWP and Reff is examined in view of changing aerosol load. Cloud
drop growth is facilitated in presence of high moisture content. This is evident
from the fact that Reff is found to broadly increase with an increase in LWP in
every season over Arabian Sea as well as over Bay of Bengal. It is also noted that
Reff is larger across a wide range of LWP in ‘clean’ condition (AOD < 0.2) and it
decreases in the ‘moderately polluted’ condition (0.2 < AOD < 0.4) and decreases
further in the ‘highly polluted’ condition and (AOD > 0.4). This clearly demonstrate
that in more polluted conditions, growth of cloud drops are restricted. This is the
evidence of classic aerosol indirect effect. However, we notice a saturation in the
decrease in Reff with an increase in AOD beyond 0.4. The results provide robust
observational evidence of aerosol-cloud interaction in the Indian Ocean region that can be
helpful in evaluating the climate model performance in representing such complex
interaction.
Keywords: Aerosol-cloud interaction, semi-direct effect, aerosol indirect effect. |
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