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|Title:||Consistent assimilation of MERIS FAPAR and atmospheric CO2 into a terrestrial vegetation model and interactive mission beneﬁt analysis|
|Authors:||KAMINSKI Thomas; KNORR Wolfgang; SCHOLZE Marko; GOBRON Nadine; PINTY Bernard; GIERING Ralf; MATHIEU Pierre Philippe|
|Citation:||BIOGEOSCIENCES vol. 9 no. 8 p. 3173–3184|
|Publisher:||COPERNICUS GESELLSCHAFT MBH|
|Type:||Articles in Journals|
|Abstract:||The terrestrial biosphere is currently a strong sink for anthropogenic CO2 emissions. Through the radiative properties of CO2, the strength of this sink has a direct inﬂuence on the radiative budget of the global climate system. The accurate assessment of this sink and its evolution under a changing climate is, hence, paramount for any efﬁcient management strategies of the terrestrial carbon sink to avoid dangerous climate change. Unfortunately, simulations of carbon and water ﬂuxes with terrestrial biosphere models exhibit large uncertainties. A considerable fraction of this uncertainty reﬂects uncertainty in the parameter values of the process formulations within the models. This paper describes the systematic calibration of the process parameters of a terrestrial biosphere model against two observational data streams: remotely sensed FAPAR (fraction of absorbed photosynthetically active radiation) provided by the MERIS (ESA’s Medium Resolution Imaging Spectrometer) sensor and in situ measurements of atmospheric CO2 provided by the GLOBALVIEW ﬂask sampling network. We use the Carbon Cycle Data Assimilation System (CCDAS) to systematically calibrate some 70 parameters of the terrestrial BETHY (Biosphere Energy Transfer Hydrology) model. The simultaneous assimilation of all observations provides parameter estimates and uncertainty ranges that are consistent with the observational information. In a subsequent step these parameter uncertainties are propagated through the model to uncertainty ranges for predicted carbon ﬂuxes. We demonstrate the consistent assimilation at global scale, where the global MERIS FAPAR product and atmospheric CO2 are used simultaneously. The assimilation improves the match to independent observations. We quantify how MERIS data improve the accuracy of the current and future (net and gross) carbon ﬂux estimates (within and beyond the assimilation period). We further demonstrate the use of an interactive mission beneﬁt analysis tool built around CCDAS to support the design of future space missions. We ﬁnd that, for long-term averages, the beneﬁt of FAPAR data is most pronounced for hydrological quantities, and moderate for quantities related to carbon ﬂuxes from ecosystems. The beneﬁt for hydrological quantities is highest for semi-arid tropical or sub-tropical regions. Length of mission or sensor resolution is of minor importance.|
|JRC Institute:||Institute for Environment and Sustainability|
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