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| Titel |
Constraints on aerosol processes in climate models from vertically-resolved aircraft observations of black carbon |
| VerfasserIn |
Z. Kipling, P. Stier, J. P. Schwarz, A. E. Perring, J. R. Spackman, G. W. Mann, C. E. Johnson, P. J. Telford |
| 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. 12 ; Nr. 13, no. 12 (2013-06-20), S.5969-5986 |
| Datensatznummer |
250018714
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| Publikation (Nr.) |
 copernicus.org/acp-13-5969-2013.pdf |
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| Zusammenfassung |
Evaluation of the aerosol schemes in current climate models is dependent upon
the available observational data. In-situ observations from flight campaigns
can provide valuable data about the vertical distribution of aerosol that is
difficult to obtain from satellite or ground-based platforms, although they
are localised in space and time. Using single-particle soot-photometer (SP2)
measurements from the HIAPER Pole-to-Pole Observations (HIPPO) campaign,
which consists of many vertical profiles over a large region of the Pacific,
we evaluate the meridional and vertical distribution of black carbon (BC)
aerosol simulated by the HadGEM3–UKCA and ECHAM5–HAM2 models. Both models
show a similar pattern of overestimating the BC column burden compared to
that derived from the observations, in many areas by an order of magnitude.
However, by sampling the simulated BC mass mixing ratio along the flight
track and comparing to the observations, we show that this discrepancy has a
rather different vertical structure in the two models: in HadGEM3–UKCA the
discrepancy is dominated by excess aerosol in the tropical upper troposphere,
while in ECHAM5–HAM2 areas of discrepancy are spread across many different
latitudes and altitudes.
Using this methodology, we conduct sensitivity tests on two specific elements
of the models: biomass-burning emissions and scavenging by convective
precipitation. We show that, by coupling the convective scavenging more
tightly with convective transport, both the column burden and vertical
distribution of BC in HadGEM3–UKCA are much improved with respect to the
observations, with a substantial and statistically significant increase in
correlation – this demonstrates the importance of a realistic representation
of this process. In contrast, updating from GFED2 to GFED3.1 biomass-burning
emissions makes a more modest improvement in both models, which is not
statistically significant. By comparing our results with a more traditional
approach using regional- and monthly-mean vertical profile curves, we show
that the point-by-point analysis allows the model improvements to be
demonstrated more clearly.
We also demonstrate the important role that nudged simulations (where the
large-scale model dynamics are continuously relaxed towards a reanalysis) can
play in this type of evaluation, allowing statistically significant
differences between configurations of the aerosol scheme to be seen where the
differences between the corresponding free-running simulations would not be
significant. |
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