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| Titel |
A regional CO2 observing system simulation experiment for the ASCENDS satellite mission |
| VerfasserIn |
J. S. Wang, S. R. Kawa, J. Eluszkiewicz, D. F. Baker, M. Mountain, J. Henderson, T. Nehrkorn, T. S. Zaccheo |
| 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 ; 14, no. 23 ; Nr. 14, no. 23 (2014-12-08), S.12897-12914 |
| Datensatznummer |
250119215
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| Publikation (Nr.) |
 copernicus.org/acp-14-12897-2014.pdf |
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| Zusammenfassung |
| Top–down estimates of the spatiotemporal variations in emissions and uptake
of CO2 will benefit from the increasing measurement density brought by
recent and future additions to the suite of in situ and remote CO2
measurement platforms. In particular, the planned NASA Active Sensing of
CO2 Emissions over Nights, Days, and Seasons (ASCENDS) satellite
mission will provide greater coverage in cloudy regions, at high latitudes,
and at night than passive satellite systems, as well as high precision and
accuracy. In a novel approach to quantifying the ability of satellite column
measurements to constrain CO2 fluxes, we use a portable library of
footprints (surface influence functions) generated by the Stochastic Time-Inverted Lagrangian Transport (STILT)
model in combination with the Weather Research and Forecasting (WRF) model in a regional Bayesian synthesis inversion. The
regional Lagrangian particle dispersion model framework is well suited to
make use of ASCENDS observations to constrain weekly fluxes in North America at a high resolution, in
this case at 1° latitude × 1° longitude. We consider random measurement errors only, modeled as a
function of the mission and instrument design specifications along with
realistic atmospheric and surface conditions. We find that the ASCENDS
observations could potentially reduce flux uncertainties substantially at
biome and finer scales. At the grid scale and weekly resolution, the largest
uncertainty reductions, on the order of 50%, occur where and when there
is good coverage by observations with low measurement errors and the a
priori uncertainties are large. Uncertainty reductions are smaller for a
1.57 μm candidate wavelength than for a 2.05 μm wavelength,
and are smaller for the higher of the two measurement error levels that we
consider (1.0 ppm vs. 0.5 ppm clear-sky error at Railroad Valley, Nevada).
Uncertainty reductions at the annual biome scale range from ~40% to ~75% across our four instrument design cases
and from ~65% to ~85% for the continent
as a whole. Tests suggest that the quantitative results are moderately
sensitive to assumptions regarding a priori uncertainties and boundary
conditions. The a posteriori flux uncertainties we obtain, ranging from 0.01
to 0.06 Pg C yr−1 across the biomes, would meet requirements for
improved understanding of long-term carbon sinks suggested by a previous
study. |
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