Project Description
Evaluation of future satellite missions for GHG surface emission retrievals
NOVELTIS has developed, in collaboration with the LSCE, a unique System Simulator of the theoretical performances of MicroCarb and MERLIN satellite missions for atmospheric GHG monitoring in terms of expected accuracy on surface fluxes at large spatial scales (500 to 1000 km).
Atmospheric carbon dioxide (CO2) and methane (CH4) are two of the most important greenhouse gases. For an increased understanding of the relationships between the carbon cycle, including anthropogenic emission, and climate change, it is crucial to be able to accurately quantify fluxes of CO2 and CH4 between the atmosphere and the Earth’s surfaces at large scales. The network of ground stations and airborne flask measurements monitor accurately and without bias the temporal evolution of these greenhouse gases (GHG) but suffer from a limited spatial coverage.
Space-borne sensors provide a more complete spatio-temporal coverage, but however at the expense of a lower measurement accuracy and the existence of systematic errors. In order to infer corresponding GHG emissions and sinks at the Earth surface, these space-borne requires assimilation system relying on chemistry transport models.
The future MicroCarb (CNES) and MERLIN (DLR-CNES) missions, scheduled for launch in 2021 and 2024, will monitor atmospheric weighted columns of carbon dioxide (XCO2) and methane (XCH4) respectively at the global scale.
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Evaluation of future satellite missions for GHG surface emission retrievals
NOVELTIS has developed a unique System Simulator of the theoretical performances of MicroCarb and MERLIN satellite missions for atmospheric GHG monitoring in terms of expected accuracy on surface fluxes at large spatial scales (500 to 1000 km).
Project details
Categories:
Atmospheric carbon dioxide (CO2) and methane (CH4) are two of the most important greenhouse gases. For an increased understanding of the relationships between the carbon cycle, including anthropogenic emission, and climate change, it is crucial to be able to accurately quantify fluxes of CO2 and CH4 between the atmosphere and the Earth’s surfaces at large scales. The network of ground stations and airborne flask measurements monitor accurately and without bias the temporal evolution of these greenhouse gases (GHG) but suffer from a limited spatial coverage.
Space-borne sensors provide a more complete spatio-temporal coverage, but however at the expense of a lower measurement accuracy and the existence of systematic errors. In order to infer corresponding GHG emissions and sinks at the Earth surface, these space-borne requires assimilation system relying on chemistry transport models.
The future MicroCarb (CNES) and MERLIN (DLR-CNES) missions, scheduled for launch in 2021 and 2024, will monitor atmospheric weighted columns of carbon dioxide (XCO2) and methane (XCH4) respectively at the global scale.
During the development phase of the missions, it is important to already assess their expected performances to reduce uncertainties on carbon dioxide / methane emissions depending on several possible scenarios of instrument characteristics and on plausible causes of random and systematic errors.
Because uncorrelated random errors statistically diminish with the time accumulation of raw satellite data, it is expected that they provide a too optimistic view of the performances of the tested observing networks to constrain surface emissions. On the contrary, systematic errors remain when accumulating data, and may ultimately limit the exploitation of satellite data to constrain surface emissions. Using OSSE provides an efficient tool to estimate the reduction of uncertainties on carbon dioxide / methane emissions that can be expected once the satellite are launched.
Means used
- NOVELTIS has developed, in collaboration with the LSCE, an OSSE that enables translating random and systematic errors on XCO2/XCH4 observations on the uncertainty reductions on surface emissions and sinks of CO2/CH4 that can be expected once the satellite is launched.
- This OSSE has been applied to the future MicroCarb and MERLIN missions in order to quantify the expected uncertainty reductions on surface CO2/CH4 fluxes.
Results
- We calculated the theoretical estimation performances of the MicroCarb and MERLIN missions and demonstrated their added value on the quantification of CO2/CH4 sources and sinks relative to current observation systems (ground network and other space-borne instruments).
- We quantified i) the impact of different instrumental configurations on the flux estimation errors and ii) the impact of several plausible causes of systematic measurement errors which could degrade the operational exploitation of the satellite data. These results should support the choice to be made when designing the operational processing chains for both instruments.
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