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| Titel |
Aerosol microphysics simulations of the Mt.~Pinatubo eruption with the UM-UKCA composition-climate model |
| VerfasserIn |
S. S. Dhomse, K. M. Emmerson, G. W. Mann, N. Bellouin, K. S. Carslaw, M. P. Chipperfield, R. Hommel, N. L. Abraham, P. Telford, P. Braesicke, M. Dalvi, C. E. Johnson, F. O'Connor, O. Morgenstern, J. A. Pyle, T. Deshler, J. M. Zawodny, L. W. Thomason |
| 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 ; 14, no. 20 ; Nr. 14, no. 20 (2014-10-24), S.11221-11246 |
| Datensatznummer |
250119119
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| Publikation (Nr.) |
 copernicus.org/acp-14-11221-2014.pdf |
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| Zusammenfassung |
We use a stratosphere–troposphere composition–climate model with
interactive sulfur chemistry and aerosol microphysics, to investigate the
effect of the 1991 Mount Pinatubo eruption on stratospheric aerosol
properties. Satellite measurements indicate that shortly after the eruption,
between 14 and 23 Tg of SO2 (7 to 11.5 Tg of
sulfur) was present in the tropical stratosphere. Best estimates of
the peak global stratospheric aerosol burden are in the range
19 to 26 Tg, or 3.7 to 6.7 Tg of sulfur assuming a composition
of between 59 and 77 % H2SO4. In light of this large uncertainty range,
we performed two main simulations with 10 and 20 Tg of
SO2 injected into the tropical lower stratosphere. Simulated
stratospheric aerosol properties through the 1991 to 1995 period are
compared against a range of available satellite and in situ
measurements. Stratospheric aerosol optical depth (sAOD) and effective radius
from both simulations show good qualitative agreement with the
observations, with the timing of peak sAOD and decay timescale
matching well with the observations in the tropics and mid-latitudes.
However, injecting 20 Tg gives a factor of 2
too high stratospheric aerosol mass burden compared to the satellite
data, with consequent strong high biases in simulated sAOD and surface
area density, with the 10 Tg injection in much better agreement.
Our model cannot explain the large fraction of the injected sulfur that the
satellite-derived SO2 and aerosol burdens indicate was removed within
the first few months after the eruption.
We suggest that either there is an additional alternative loss
pathway for the SO2 not included in our model (e.g. via
accommodation into ash or ice in the volcanic cloud) or that a larger
proportion of the injected sulfur was removed via cross-tropopause
transport than in our simulations.
We also critically evaluate the simulated evolution of the particle size
distribution, comparing in detail to
balloon-borne optical particle counter (OPC) measurements from Laramie, Wyoming, USA (41° N).
Overall, the model captures remarkably well the complex
variations in particle concentration profiles across the different
OPC size channels. However, for the 19 to 27 km injection height-range
used here, both runs have a modest high bias in the lowermost stratosphere
for the finest particles (radii less than 250 nm), and the decay timescale is
longer in the model for these particles, with a much later return
to background conditions. Also, whereas the 10 Tg run compared best to
the satellite measurements, a significant low bias is apparent in the coarser size
channels in the volcanically perturbed lower stratosphere.
Overall, our results suggest that, with appropriate calibration,
aerosol microphysics models are capable of capturing the observed variation in
particle size distribution in the stratosphere across both volcanically
perturbed and quiescent conditions. Furthermore, additional
sensitivity simulations suggest that predictions with the models are
robust to uncertainties in sub-grid particle formation
and nucleation rates in the stratosphere. |
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