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| Titel |
Influence of model resolution on the atmospheric transport of 10Be |
| VerfasserIn |
U. Heikkilä, A. M. Smith |
| 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 ; 12, no. 21 ; Nr. 12, no. 21 (2012-11-13), S.10601-10612 |
| Datensatznummer |
250011585
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| Publikation (Nr.) |
 copernicus.org/acp-12-10601-2012.pdf |
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| Zusammenfassung |
| Understanding the transport path of the solar activity proxy 10Be from
source to archive is crucial for the interpretation of its observed
variability. The extent of mixing of the strong production signal has been
quantified in a previous study (Heikkilä et al., 2009). In this study we
perform sensitivity studies to investigate the influence of model resolution
on the degree of mixing and transport path of 10Be in the atmosphere
using the ECHAM5-HAM aerosol-climate model. This study permits us to choose
an acceptable resolution, and so minimum CPU time, to produce reconstructions
as physically accurate as possible. Five model resolutions are applied:
T21L19: a coarse horizontal and vertical resolution with model top at ca.
30 km, T42L31: an average horizontal and fine vertical one, T42L39:
similar vertical resolution than L19 but including the middle atmosphere up
to ca. 80 km, T63L31: a fine horizontal and vertical resolution and
T63L47: a fine resolution horizontally and vertically with middle atmosphere.
Comparison with observations suggests that a finer horizontal and vertical
resolution might be beneficial, producing a reduced meridional gradient,
although the spread between observations was much larger than between the
five model runs. In terms of atmospheric mixing the differences became more
distinguishable. All resolutions agreed that the main driver of deposition
variability, observed in natural archives, is the input of stratospheric
10Be (total contribution 68%) which is transported into the
troposphere at latitudes 30–50°. In the troposphere the model
resolutions deviated largely in the dispersion of the stratospheric component
over latitude. The finest resolution (T63L47) predicted the least dispersion
towards low latitudes but the most towards the poles, whereas the coarsest
resolution (T21L19) suggested the opposite. The tropospheric components of
10Be differed less between the five model runs. The largest differences
were found in the polar tropospheric components, which contribute the least
to total production (≈ 4%). We conclude that the use of the T42
horizontal resolution seems to be sufficient in terms of atmospheric mixing
of a stratospheric tracer because no substantial improvement was seen when
the resolution was increased from T42 to T63. The use of the middle
atmospheric configuration is a trade-off between correctly describing
stratospheric dynamics and having to reduce vertical resolution. The use of a
high vertical resolution seemed more beneficial than the middle atmospheric
configuration in this study. The differences found between the T42L31 and
T63L31 resolutions were so small that T42L31 is a good choice because of its
computational efficiency. |
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