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| Titel |
Modeling of 2008 Kasatochi volcanic sulfate direct radiative forcing: assimilation of OMI SO2 plume height data and comparison with MODIS and CALIOP observations |
| VerfasserIn |
J. Wang, S. Park, J. Zeng, C. Ge, K. Yang, S. Carn, N. Krotkov, A. H. Omar |
| 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 ; 13, no. 4 ; Nr. 13, no. 4 (2013-02-19), S.1895-1912 |
| Datensatznummer |
250017666
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| Publikation (Nr.) |
 copernicus.org/acp-13-1895-2013.pdf |
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| Zusammenfassung |
| Volcanic SO2 column amount and injection height retrieved from the
Ozone Monitoring Instrument (OMI) with the Extended Iterative Spectral
Fitting (EISF) technique are used to initialize a global chemistry transport
model (GEOS-Chem) to simulate the atmospheric transport and lifecycle of
volcanic SO2 and sulfate aerosol from the 2008 Kasatochi eruption, and
to subsequently estimate the direct shortwave, top-of-the-atmosphere
radiative forcing of the volcanic sulfate aerosol. Analysis shows that the
integrated use of OMI SO2 plume height in GEOS-Chem yields: (a) good
agreement of the temporal evolution of 3-D volcanic sulfate distributions
between model simulations and satellite observations from the Moderate
Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar with
Orthogonal Polarisation (CALIOP), and (b) an e-folding time for volcanic
SO2 that is consistent with OMI measurements, reflecting SO2
oxidation in the upper troposphere and stratosphere is reliably represented
in the model. However, a consistent (~25%) low bias is
found in the GEOS-Chem simulated SO2 burden, and is likely due to a
high (~20%) bias of cloud liquid water amount (as compared
to the MODIS cloud product) and the resultant stronger SO2 oxidation
in the GEOS meteorological data during the first week after eruption when
part of SO2 underwent aqueous-phase oxidation in clouds. Radiative
transfer calculations show that the forcing by Kasatochi volcanic sulfate
aerosol becomes negligible 6 months after the eruption, but its global
average over the first month is −1.3 Wm−2, with the majority of the
forcing-influenced region located north of 20° N, and with
daily peak values up to −2 Wm−2 on days 16–17. Sensitivity experiments
show that every 2 km decrease of SO2 injection height in the GEOS-Chem
simulations will result in a ~25 % decrease in volcanic
sulfate forcing; similar sensitivity but opposite sign also holds for a
0.03 μm increase of geometric radius of the volcanic aerosol particles.
Both sensitivities highlight the need to characterize the SO2 plume
height and aerosol particle size from space. While more research efforts are
warranted, this study is among the first to assimilate both satellite-based
SO2 plume height and amount into a chemical transport model for an
improved simulation of volcanic SO2 and sulfate transport. |
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