SCIAMACHYによる全球におけるメタン発生地の分布抽出

摘要

世界の平均温度は2005年を基準に100年間で0.74±0.18°上昇している(IPCC,2007)。地球温暖化が進行すると長期的には気温や降水量が変化し，短期的には異常気象の発生頻度や強度が変化する。特に異常気象は一旦発生すると被害も甚大になることが多いため，温暖化影響解析においても重要な検討課題となっている(Trenberth and Shea, 2005)。%Since the beginning of the industrial revolution, the atmospheric concentration of carbon dioxide (CO_2) has increased by nearly 41%, and the Methane (CH_4) concentration has increased more than double. CH_4 is the second most important greenhouse gas, following CO_2. 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 CH_4 source area is extracted by estimating the emission as the difference between CH_4 concentration in time series observed by SCIAMACHY and the background concentrations of CH_4. Missing data of CH_4 concentration by cloud are interpolated both spatially and temporally. It is assumed that CH_4 concentration is negligible over ocean and that the CH_4 concentration over the ocean is due to the advection of CH_4 from the land. The background concentration of CH_4 on the land was defined as CH_4 concentration over the ocean in the same latitude. The estimated CH_4 emissions from the land exhibited the source of CH_4 are not only in paddy fields but also in broadleaf evergreen area in South America and Central Africa.