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| Titel |
Greenhouse gas network design using backward Lagrangian particle dispersion modelling – Part 2: Sensitivity analyses and South African test case |
| VerfasserIn |
A. Nickless, T. Ziehn, P. J. Rayner, R. J. Scholes, F. Engelbrecht |
| 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 ; 15, no. 4 ; Nr. 15, no. 4 (2015-02-25), S.2051-2069 |
| Datensatznummer |
250119459
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| Publikation (Nr.) |
 copernicus.org/acp-15-2051-2015.pdf |
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| Zusammenfassung |
This is the second part of a two-part paper considering a measurement network
design based on a stochastic Lagrangian particle dispersion model (LPDM) developed
by Marek Uliasz, in this case for South Africa.
A sensitivity analysis was performed for different specifications of the
network design parameters which were applied to this South African test case.
The LPDM, which can be used to derive the sensitivity matrix used in an
atmospheric inversion, was run for each candidate station for the months of
July (representative of the Southern Hemisphere winter) and January (summer).
The network optimisation procedure was carried out under a standard set of
conditions, similar to those applied to the Australian test case in Part 1,
for both months and for the combined 2 months, using the incremental
optimisation (IO) routine. The optimal network design setup was subtly
changed, one parameter at a time, and the optimisation routine was re-run under
each set of modified conditions and compared to the original optimal network
design. The assessment of the similarity between network solutions showed
that changing the height of the surface grid cells, including an uncertainty
estimate for the ocean fluxes, or increasing the night-time observation error
uncertainty did not result in any significant changes in the positioning of
the stations relative to the standard design. However, changing the prior
flux error covariance matrix, or increasing the spatial resolution, did.
Large aggregation errors were calculated for a number of candidate
measurement sites using the resolution of the standard network design.
Spatial resolution of the prior fluxes should be kept as close to the
resolution of the transport model as the computing system can manage, to
mitigate the exclusion of sites which could potentially be beneficial to the
network. Including a generic correlation structure in the prior flux error
covariance matrix led to pronounced changes in the network solution. The
genetic algorithm (GA) was able to find a marginally better solution than the
IO procedure, increasing uncertainty reduction by 0.3 %, but still included
the most influential stations from the standard network design. In addition,
the computational cost of the GA compared to IO was much higher. Overall the
results suggest that a good improvement in knowledge of South African fluxes
is available from a feasible atmospheric network, and that the general
features of this network are invariable under several reasonable choices in
a network design study. |
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