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| Titel |
Ship Emission Influence on Clouds: A Sensitivity Assessment of ECHAM5-HAM |
| VerfasserIn |
Karsten Peters, Johannes Quaas, Philip Stier |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041628
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| Zusammenfassung |
| Clouds are of importance in the climate system because of their interaction with the
hydrological cycle and the radiant energy flow. Anthropogenic activities come in hand with
emissions of aerosols and aerosol precursor gases, making the quantification of their impact
on cloud properties, e.g. cloud droplet number concentration, cloud lifetime or even cloud top
height, a topic of ongoing research. Aerosol influence on cloud micro- and macrophysical
properties are referred to as aerosol indirect effects and are subject to the largest uncertainties
of all radiative forcing components of the Earth System when it comes to assessing
human induced climate change. Seagoing ships are the least regulated sources of
anthropogenic emissions, burning low-quality residual fuels containing high amounts of
sulfur or even heavy metals. Combustion of such fuels produces, aside from gaseous
species, large amounts of particulate matter (PM) consisting of elemental (black) and
organic carbon, sulfate, ash and particles forming from sulfuric acid. The emitted
particles can serve as cloud condensation nuclei (CCN) leading to aerosol indirect
effects.
In this study, we investigate the sensitivity of aerosol indirect effects as calculated by
the ECHAM5-HAM aerosol-climate model with respect to ship emissions. The
model is run for seven years (including a two year spinup, five years averaging for
results) with a spatial resolution of 2.8- x 2.8- and prescribed sea surface properties
(AMIP). We use parametrizations of aerosol cloud interactions to investigate aerosol
indirect effects. Aerosol emissions from ships are provided by the recently compiled
QUANTIFY emission inventory. The sensitivity runs performed use the emission
of black carbon (BC) and sulfur dioxide (SO2) increased by a factor of 10(100),
enabling a focus on the aerosol-cloud interactions when the marine boundary layer
composition is significantly disturbed. Furthermore, experiments using increased BC(SO2)
and unchanged SO2(BC) emissions are performed to analyse component specific
sensitivity. Dependency of calculated aerosol indirect effects on model resolution is also
investigated.
Results show, that spatial patterns of changes in cloud micro- and macrophysical
properties as well as radiative effects do not indicate the presence of elevated levels of aerosol
burdens in shipping corridors on global oceans. It is by an increase of the emissions by a
factor of 10 that patterns begin to show. These are enhanced when increasing the emissions
by a factor of 100. As expected, effects on cloud properties are significantly dependent on the
presence of soluble particles and can only be depicted when artificially high ship emissions
are implemented in the model. This hints at the necessity to further investigate and
modify the parametrization of the interaction of ship emitted particles and trace
gases. |
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