SCIAMACHYによる全球におけるメタン発生地の分布抽出

抄録

Since the beginning of the industrial revolution, the atmospheric concentration of carbon dioxide (CO₂) has increased by nearly 41%, and the Methane (CH₄) concentration has increased more than double. CH₄ is the second most important greenhouse gas, following CO₂. Emissions, extrapolated from measurements of actual gas flux from wetlands, vary from place to place, even within the same wetland. This high variability makes large-scale estimates difficult and means that average emissions levels include a large degree of estimated uncertainty. The SCIAMACHY instrument on the European Space Agency satellite ENVISAT measured greenhouse gases in the troposphere and stratosphere. In this study, the CH₄ source area is extracted by estimating the emission as the difference between CH₄ concentration in time series observed by SCIAMACHY and the background concentrations of CH₄. Missing data of CH₄ concentration by cloud are interpolated both spatially and temporally. It is assumed that CH₄ concentration is negligible over ocean and that the CH₄ concentration over the ocean is due to the advection of CH₄ from the land. The background concentration of CH₄ on the land was defined as CH₄ concentration over the ocean in the same latitude. The estimated CH₄ emissions from the land exhibited the source of CH₄ are not only in paddy fields but also in broadleaf evergreen area in South America and Central Africa.