CGER Reports

CGER’S SUPERCOMPUTER MONOGRAPH REPORT Vol.15 Algorithms for carbon flux estimation using GOSAT observational data

The Greenhouse gases Observing SATellite (GOSAT) was placed in orbit in January 2009 to ascertain the global distribution of the two major greenhouse gases, carbon dioxide (CO2) and methane, and to understand how the sources and sinks (fluxes) of these gases vary with seasons, years, and geographical locations. To this end, an inverse modeling system that estimates CO2 regional fluxes from the GOSAT observations is being developed and tested using the supercomputing facility at NIES.

This volume of the CGER's Supercomputer Monograph Report describes the main components of the inverse modeling system. The system consists of tracer transport models for the atmosphere (Figure 1) and ocean, process models of the carbon cycle in the terrestrial biosphere (Figure 2) and ocean, and inventories of anthropogenic and natural fluxes (Figure 3). Also included in this volume, other than the descriptions of the components, is a report which shows the degree of contribution that the GOSAT data would make in improving the accuracy of surface CO2 fluxes estimated monthly on a sub-continental scale (Figure 4).

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Figure 1. Surface CO2 concentrations (in ppm) simulated with NIES atmospheric tracer transport model (August 30, 2002).

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Figure 2. Diurnal and seasonal patterns of observed (left) and model-predicted (right) net ecosystem CO2 exchange (NEE) at ten selected sites (given in ┬Ámol CO2 m-2 s-1). The magnitudes of half-hourly NEE are represented by colors.

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Figure 3. Growingseason net fluxes (GSNF) of the terrestrial biosphere (latitudinal averages given in Pg C year-1) optimized with partial-column and near-surface CO2 observation data.

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Figure 4. Uncertainties of estimated CO2 fluxes (given in GtC yr-1 region-1). Left: CO2 fluxes estimated only from surface CO2 observation data. Right: Fluxes estimated from surface observation data and GOSAT data.