Showing papers by "Tomohiro Oda published in 2015"

An intercomparison of inverse models for estimating sources and sinks of CO2 using GOSAT measurements

Abstract: This study presents the outcome of an inverse modeling intercomparison experiment on the use of total column CO2 retrievals from Greenhouse Gas Observing Satellite (GOSAT) for quantifying global sources and sinks of CO2. Eight research groups submitted inverse modeling results for the first year of GOSAT measurements. Inversions were carried out using only GOSAT data, a combination of GOSAT and surface measurements, and using only surface measurements. As expected, the most robust flux estimates are obtained at large scales (e.g., within 20% of the annual flux at the global scale), and they quickly diverge toward the scale of the subcontinental TRANSCOM regions and beyond (to >100% of the annual flux). We focus our analysis on a shift in the CO2 uptake over land from the Tropics toward the Northern Hemisphere Extra tropics of ∼1 PgC/yr when GOSAT data are used in the inversions. This shift is largely driven by TRANSCOM regions Europe and Northern Africa, showing, respectively, an increased uptake and release of 0.7 and 0.9 PgC/yr. Inversions using GOSAT data show a reduced gradient between midlatitudes of the Northern Hemisphere and the Tropics, consistent with the latitudinal shift in carbon uptake. However, the reduced gradients degrade the agreement with background aircraft and surface measurements. To narrow the range of inversion-derived flux, estimates will require further efforts to understand the differences not only between the retrieval schemes but also between inverse models, as their contributions to the overall uncertainty are estimated to be of similar magnitude.

Uncertainty associated with fossil fuel carbon dioxide (CO2) gridded emission datasets

Abstract: CO2 emissions from fossil fuel combustion (FFCO2) serves as a reference in carbon budget analysis and thus needs to be accurately quantified. FFCO2 estimates from different emission inventories often agree well at global and national level, however their subnational emission spatial distributions are unique and subject to uncertainty in the proxy data used for disaggregation of country emissions. In this study, we attempt to assess the uncertainty associated with emission spatial distributions in gridded FFCO2 emission inventories. We compared emission distributions from four gridded inventories at a 1 W 1 degree resolution and used the differences as a proxy for uncertainty. The calculated uncertainties typically range from 30% to 200% and inversely correlated with the emission magnitude. We also discuss limitations of our approach and possible difficulties when implemented at a higher spatial resolution.

Spatial Greenhouse Gas (GHG) inventory and uncertainty analysis: A case study for electricity generation in Poland and Ukraine

Abstract: Spatial inventory of greenhouse gas (GHG) emissions allows to identify emission changes in space. In this study we have analyzed the specificity of territorial distribution of GHG emission sources for Poland and Ukraine. Mathematical models and geoinformation technology for spatial analysis of GHG emissions from fuel consumption by power and combined heat and power plants have been improved by taking into account uncertainty of input parameters and specific factors for every separate electricity/heat generating companies. We have updated the input digital maps of emission point sources. Based on it, we have developed a spatial GHG emission distribution for 2012. The uncertainties of GHG emissions in CO2-equivalent for the power plants which we consider in our study are asymmetric and the upper bounds of 95% confidence intervals do not exceed 20,3%.