Abstract
The second NASA Earth Venture Mission, Geostationary Carbon Cycle Observatory (GeoCarb), will provide measurements of atmospheric carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), and solar-induced fluorescence (SIF) from Geostationary Orbit (GEO). The GeoCarb mission will deliver daily maps of column concentrations of CO2, CH4, and CO over the observed landmasses in the Americas at a spatial resolution of roughly 10 x 10 km. Persistent measurements of CO2, CH4, CO, and SIF will contribute significantly to resolving carbon emissions and illuminating biotic processes at urban to continental scales, which will allow the improvement of modeled biogeochemical processes in Earth System Models as well as monitor the response of the biosphere to disturbance. This is essential to improve understanding of the Carbon-Climate connection. In this paper, we introduce the instrument and the GeoCarb Mission, and we demonstrate the potential scientific contribution of the mission through a series of CO2 and CH4 simulation experiments. We find that GeoCarb will be able to constrain emissions at urban to continental spatial scales on weekly to annual time scales. The GeoCarb mission particularly builds upon the Orbiting Carbon Obserevatory-2 (OCO-2), which is flying in Low Earth Orbit.
Highlights
Global trends in the atmospheric concentrations of carbon dioxide (CO2) and methane (CH4) are well established
TM5-4DVAR was employed to compute the expected uncertainty reduction in surface fluxes for this hypothesis. In this Observing Systems Simulation Experiments (OSSEs), the ensemble of prior fluxes is composed of statistical perturbations of truth fluxes that is built from the Carnegie-Ames-Stanford Approach (CASA, Potter et al, 1993) biogenic fluxes and the Global Fire Emissions Database Version 3 for fire fluxes (GFEDv3, Takahashi et al, 2009; van der Werf et al, 2010) for ocean fluxes, and fossil fuel emissions from the Carbon Dioxide Information Analysis Center (CDIAC, Andres et al, 2015)
By carefully connecting measurement requirements to flux uncertainties, we have demonstrated the potential for Geostationary Carbon Cycle Observatory (GeoCarb) to revolutionize our understanding of the carbon cycle using the OSSEs detailed above
Summary
Global trends in the atmospheric concentrations of carbon dioxide (CO2) and methane (CH4) are well established. The Geostationary Carbon Observatory: GeoCarb a relatively coarse spatial footprint (100 km2) and three-day revisit cycle, GOSAT was designed to make measurements that would constrain the carbon cycle at large scales in regions that are unobservable in the surface network, such as the tropical oceans. The Orbiting Carbon Observatory-2 (OCO-2) is a 3-channel spectrometer, which measures the concentration of atmospheric carbon dioxide. It was successfully launched in 2014 to provide regular global coverage at high spatial resolution to better sample atmospheric CO2 with the objective, like GOSAT, of providing a top-down constraint on surface fluxes. GeoCarb is a 4-channel, slit-scan spectrometer that will measure absorption spectra at wavelengths 1.61, 2.06, and 2.32 μm in sunlight reflected from the land to retrieve total atmosphere-column amounts of CO2, CH4, and carbon monoxide (CO) from GEOstationary orbit (GEO). We provide an outline of the GeoCarb mission and some simulation studies that indicate the potential for a transformative set of measurements, as well as pointing to some of the issues to be resolved before GeoCarb launches in 2022
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