Tohoku University · Environmental Science
Professor Shinji Morimoto's research lab specializes in atmospheric chemistry and environmental science, focusing on the isotopic composition of greenhouse gases such as methane (CH₄) and carbon dioxide (CO₂) to understand their sources, sinks, and global budgets. The lab employs advanced atmospheric inversion techniques and long-term observational data from remote sites like Ny Ålesund, Svalbard, to investigate temporal and spatial variations in trace gases and their isotopes. Key research directions include the use of carbon and nitrogen isotope ratios (e.g., δ¹³C, δ¹⁵N) to constrain emission sources, particularly microbial and anthropogenic contributions, and to improve the accuracy of global carbon cycle modeling. The lab also conducts high-altitude balloon sampling to study stratospheric transport and atmospheric age of air, contributing to a deeper understanding of atmospheric dynamics and composition.
Figures are computed from collected data and may differ slightly.
Abstract. We have constructed an atmospheric inversion framework based on TM5-4DVAR to jointly assimilate measurements of methane and δ13C of methane in order to estimate source-specific methane emissions. Here we present global emission estimates from this framework for the period 1999–2016. We assimilate a newly constructed, multi-agency database of CH4 and δ13C measurements. We find that traditional CH4-only atmospheric inversions are unlikely to estimate emissions consistent with atmospheric
Net CO 2 fluxes between the atmosphere and the ocean, and between the atmosphere and the terrestrial biosphere, were estimated by constraining a two‐dimensional atmospheric transport model with the CO 2 concentration and its δ 13 C data obtained from our shipboard measurements in the western Pacific region during the period April 1984 to December 1991. The results obtained for the non‐El Niño and Southern Oscillation (ENSO) years during this time period showed that the ocean acted as a CO 2 sink
Systematic observations of the atmospheric CH 4 mole fraction and its carbon isotope ratio δ 13 CH 4 have been carried out at Ny Ålesund, Svalbard (78°55′N, 11°56′E) since 1991 and 1996, respectively. The CH 4 and δ 13 CH 4 showed clear seasonal cycles with respective peak‐to‐peak amplitudes of 48 ppb and 0.42‰. By comparing the anomalies in the increase rate of the CH 4 with those of δ 13 CH 4 , it is suggested that the cause of the rapid increase in the CH 4 mole fraction observed at Ny Ålesun
We have conducted systematic observations of the CH4 mole fraction and its carbon isotope ratio (δ13C) at Ny-Ålesund, Svalbard (78°55′N, 11°56′E) using air samples collected weekly since 1991 and 1996, respectively. The CH4 mole fraction showed long-term increase until 1999, stagnation between 2000 and 2006, followed by an increase after 2006. On the other hand, δ13C showed monotonous increase until 2006 and decrease after 2006. By comparing the rates of change in the CH4 mole fraction and δ13C
Abstract. The gravitational separation of major atmospheric components, in addition to the age of air, would provide additional useful information about stratospheric circulation. However, observations of the age of air and gravitational separation are still geographically sparse, especially in the tropics. In order to address this issue, air samples were collected over Biak, Indonesia in February 2015 using four large plastic balloons, each loaded with two compact cryogenic samplers. With a ver
Abstract. A study was conducted to compare the δ(O2/N2) scales used by four laboratories engaged in atmospheric δ(O2/N2) measurements. These laboratories are the Research Institute for Environmental Management Technology, Advanced Industrial Science and Technology (EMRI/AIST); the National Institute for Environmental Studies (NIES); Tohoku University (TU); and Scripps Institution of Oceanography (SIO). Therefore, five high-precision standard mixtures for the O2 molar fraction gravimetrically pre
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