 |
| Titel |
Inverse modeling of CO2 sources and sinks using satellite data: a synthetic inter-comparison of measurement techniques and their performance as a function of space and time |
| VerfasserIn |
S. Houweling, F.-M. Bréon, I. Aben, C. Rödenbeck, M. Gloor, M. Heimann, P. Ciais |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 2 ; Nr. 4, no. 2 (2004-03-25), S.523-538 |
| Datensatznummer |
250001609
|
| Publikation (Nr.) |
 copernicus.org/acp-4-523-2004.pdf |
|
|
|
|
|
| Zusammenfassung |
| Currently two polar orbiting satellite instruments measure CO2
concentrations in the Earth's atmosphere, while other missions are planned
for the coming years. In the future such instruments might become powerful
tools for monitoring changes in the atmospheric CO2 abundance and to
improve our quantitative understanding of the leading processes controlling
this. At the moment, however, we are still in an exploratory phase where
first experiences are collected and promising new space-based measurement
concepts are investigated. This study assesses the potential of some of these
concepts to improve CO2 source and sink estimates obtained from
inverse modelling. For this purpose the performance of existing and planned
satellite instruments is quantified by synthetic simulations of their ability
to reduce the uncertainty of the current source and sink estimates in
comparison with the existing ground-based network of sampling sites. Our high
resolution inversion of sources and sinks (at
8°x10°) allows us to investigate the variation of
instrument performance in space and time and at various temporal and spatial
scales. The results of our synthetic tests clearly indicate that the
satellite performance increases with increasing sensitivity of the instrument
to CO2 near the Earth's surface, favoring the near infra-red
technique. Thermal infrared instruments, on the contrary, reach a better
global coverage, because the performance in the near infrared is reduced over
the oceans owing to a low surface albedo. Near infra-red sounders can
compensate for this by measuring in sun-glint, which will allow accurate
measurements over the oceans, at the cost, however, of a lower measurement
density. Overall, the sun-glint pointing near infrared instrument is the most
promising concept of those tested. We show that the ability of satellite
instruments to resolve fluxes at smaller temporal and spatial scales is also
related to surface sensitivity. All the satellite instruments performed
relatively well over the continents resulting mainly from the larger prior
flux uncertainties over land than over the oceans. In addition, the surface
networks are rather sparse over land increasing the additional benefit of
satellite measurements there. Globally, challenging satellite instrument
precisions are needed to compete with the current surface network
(about 1ppm for weekly and 8°x10° averaged SCIAMACHY
columns). Regionally, however, these requirements relax considerably,
increasing to 5ppm for SCIAMACHY over tropical continents. This
points not only to an interesting research area using SCIAMACHY data, but
also to the fact that satellite requirements should not be quantified by only
a single number. The applicability of our synthetic results to real satellite
instruments is limited by rather crude representations of instrument and data
retrieval related uncertainties. This should receive high priority in future
work. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|