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| Titel |
Emergence of a tracer source from air concentration measurements, a new strategy for linear assimilation |
| VerfasserIn |
J.-P. Issartel |
| 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 ; 5, no. 1 ; Nr. 5, no. 1 (2005-02-02), S.249-273 |
| Datensatznummer |
250002221
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| Publikation (Nr.) |
 copernicus.org/acp-5-249-2005.pdf |
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| Zusammenfassung |
| The measurement of atmospheric concentrations by a monitoring network is a
promising tool for the identification of the widespread sources of trace
species. The paper addresses the case of the species scattered linearly by a
known meteorology. The question is classical: what can be said about the
source from a set of measurements? Is it possible to guess from the values
observed by the measurements that the source is spread close to the
detectors, or that the tracer comes from a remote region? And, if the source
was a point source, would it be possible to understand it by just considering
these values? A part of the answers is a matter of practical sense: the
resolution with which an emission can be retrieved will always be limited and
probably lower for a remote region, even if the detectors and dispersion
model are error free. The paper proposes a linear strategy of inference: to
any set of values taken by the observed concentrations is associated linearly
an estimate of the source. Doubled values lead to a doubled estimate. The
method, based on adjoint techniques, is intended to optimise the resolution
by quantifying, with the concept of illumination, which regions are well,
poorly or not seen at all. The illumination tied to ordinary adjoint
functions becomes excessive close to the detectors thus leading to inversion
artefacts. This may be corrected by attributing each point of the space time
domain a geometric and statistical weight. The adjoint functions are
transformed. The choice of this renormalising function is constrained by an
unambiguous entropic criterion preventing any overestimation of the available
information that would lead to artefacts. It amounts to evenly distribute the
information between the points organised with their weights as a "known
domain". The theory is illustrated by calculations performed with the
experimental source ETEX1. |
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