[U-01_1AM2] Forum for Global Data Sciences in Earth and Planetary Research

★ [U01-07] ボトムアップとトップダウンアプローチを併用した東アジアにおける森林火災からのCO2と水田からのCH4発生量の解析

今須 良一¹、竹内 渉²、関山 絢子²、齋藤 尚子³、*松見 豊⁴、川崎 昌博⁴、林田 佐智子⁵、小野 朗子⁵ (1.東京大学大気海洋研究所、2.東京大学生産技術研究所、3.千葉大学環境リモートセンシング研究センター、4.名古屋大学太陽地球環境研究所、5.奈良女子大学)

キーワード：二酸化炭素, メタン, GOSAT, トップダウンアプローチ, ボトムアップアプローチ, 地上リモートセンシング

There has been still a large discrepancy in estimations between bottom-up and top-down approaches for both CO₂ emissions from biomass burning and CH4 from rice paddy in East Asia. The purpose of this study is to update the emission inventory databases as to be more consistent between these two approaches through a synergetic usage of satellite data, ground-based remote sensing measurements, and in situ data. The most important parameter to estimate total CO₂ emissions from biomass burning is the biomass amount of the forests. In this study the amount is estimated based on the normalized vegetation index (NDVI) observed by satellites and, CO₂ emissions from burning area are estimated by multiplying the fire strength evaluated from hot spot data with some auxiliary data such as soil moisture and groundwater level. As for the top-down approach, CO₂ concentration data observed from space are useful for constraining the inverse analysis of CO₂ emission strength. The greenhouse gas observing satellite (GOSAT) dedicated to observe atmospheric CO₂ and CH₄ concentrations was launched in 2009 and has been operated for more than five years. The main band of its sensor can measure the columnar CO₂ concentration, however, it cannot be directly converted into the concentration near the surface. One of our attempts is to develop a retrieval method to estimate CO₂ concentration in the lower troposphere, particularly in the boundary layer, from a synergy of spectrum data in a wide spectral range covering from short wavelength infrared to the thermal infrared. In order to validate this method we have carried out CO₂ sonde observations around Tokyo city where GOSAT has been operated in a specific observation mode (targeting mode) to obtain sufficient number of data over this area. Based on the validated results, this method will be applied to analyze the data observed in biomass burning areas. One of our important targets is Kalimantan (Indonesia) where peat fire is the main CO₂ emission source. We started the ground-based measurement of columnar CO₂ concentration using an optical spectrum analyzer (OSA), and expect that these temporally continuous data would be effective for achieving the consistency between bottom-up and top-down approaches. Also started are observations of columnar CH₄ concentration using the same type of spectrometer in Sichuan basin (China) and Karnal (India) where are identified as the extremely high CH₄ concentration area based on the almost decadal record of observations by SCIAMACHY and GOSAT. It is expected that the synergetic analysis of data from satellite and ground-based measurements could contribute to make clear the cause of high concentration of CH₄ in these areas.