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CH4-emission estimation from different sources using the present GOSAT and the next-generation imaging-spectrometer suites
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  • Akihiko Kuze,
  • Hiroshi Suto,
  • Nobuhiro Kikuchi,
  • Kei Shiomi,
  • Fumie Kataoka,
  • Yutaka Kondo,
  • Takahiro Kawashima,
  • Shigetaka Mori
Akihiko Kuze
JAXA Japan Aerospace Exploration Agency

Corresponding Author:[email protected]

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Hiroshi Suto
Japan Aerospace Exploration Agency
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Nobuhiro Kikuchi
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Kei Shiomi
Earth Obs. Res. Cntr. / JAXA
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Fumie Kataoka
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Yutaka Kondo
National Institute of Polar Research
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Takahiro Kawashima
RESTEC Remote Sensing Technology Center of Japan
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Shigetaka Mori
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The Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT) was launched in Jan. 2009 to monitor global CO2 and CH4 distribution from space. The wide-spectral-range data by FTS can measure the partial-column density of the lower troposphere using sun-light reflected from the surface and thermal emission from the atmosphere. In addition to nominal global grid-observation, TANSO-FTS has an agile pointing system to target various CH4 point-sources as well as reference points every three days over years, and can capture the entire flux emitted vertically and horizontally from the source. We demonstrated the monitoring capability by using the natural-gas blowout event at Aliso Canyon, CA and tried to estimate the CH4 flux from a dairy farm in Chino, CA with the Weather Research and Forecasting model. The GOSAT footprint, which is much larger than the point-source area, reduces the enhancement of the retrieved column density close to the detection level. As the single-pixel data and acquisition time of 4 s by FTS limits the number of sampling points near the emission source, careful screening with wind speed and direction is required to acquire reference and source dataset for analysis. The largely fluctuated single data requires to be averaged to improve the precision, but the GOSAT data is spatially too sparse. We calculated the local CH4 flux from Chino using the correlation between wind speed and density, but the lack of a proper reference result in large errors. To solve the above-mentioned issues, we manufactured airborne imaging-spectrometer suites comprising two bands to measure CH4 and CO2 at 1.6 μm and O2 at 0.76 μm. They have 4,000 times more data than GOSAT, increase enhancement with higher spatial resolution, and select proper upwind reference with imaging capability. In Feb. 2018, we flew over greater Nagoya with the mixture of possible emission sources such as energy production, waste water, dairy farm, and agriculture. The spectral image of spatial resolution <100 m has clearly detected enhancement from individual local sources of CH4 and CO2. We add one more spectrometer to measure short-lived NO2 to detect plume orientation. Our goal is to individually estimate city-level CH4 flux from different source sectors.