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| Titel |
2-D reconstruction of atmospheric concentration peaks from horizontal long path DOAS tomographic measurements: parametrisation and geometry within a discrete approach |
| VerfasserIn |
A. Hartl, B. C. Song, I. Pundt |
| 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 ; 6, no. 3 ; Nr. 6, no. 3 (2006-03-17), S.847-861 |
| Datensatznummer |
250003526
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| Publikation (Nr.) |
 copernicus.org/acp-6-847-2006.pdf |
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| Zusammenfassung |
| In this study, we theoretically investigate the reconstruction of 2-D cross
sections through Gaussian concentration distributions, e.g. emission plumes,
from long path DOAS measurements along a limited number of light paths. This
is done systematically with respect to the extension of the up to four peaks
and for six different measurement setups with 2-4 telescopes and 36 light
paths each. We distinguish between cases with and without additional
background concentrations. Our approach parametrises the unknown
distribution by local piecewise constant or linear functions on a regular
grid and solves the resulting discrete, linear system by a least squares
minimum norm principle. We show that the linear parametrisation not only
allows better representation of the distributions in terms of discretisation
errors, but also better inversion of the system. We calculate area integrals
of the concentration field (i.e. total emissions rates for non-vanishing
perpendicular wind speed components) and show that reconstruction errors and
reconstructed area integrals within the peaks for narrow distributions
crucially depend on the resolution of the reconstruction grid. A recently
suggested grid translation method for the piecewise constant basis
functions, combining reconstructions from several shifted grids, is modified
for the linear basis functions and proven to reduce overall reconstruction
errors, but not the uncertainty of concentration integrals. We suggest a
procedure to subtract additional background concentration fields before
inversion. We find large differences in reconstruction quality between the
geometries and conclude that, in general, for a constant number of light
paths increasing the number of telescopes leads to better reconstruction
results. It appears that geometries that give better results for negligible
measurement errors and parts of the geometry that are better resolved are
also less sensitive to increasing measurement errors. |
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