Preprints
https://doi.org/10.5194/acp-2020-1239
https://doi.org/10.5194/acp-2020-1239

  23 Dec 2020

23 Dec 2020

Review status: this preprint is currently under review for the journal ACP.

Estimation of fire-induced carbon emission from Equatorial Asia in 2015 by using in situ aircraft and ship observations

Yosuke Niwa1,2, Yousuke Sawa2,a, Hideki Nara1, Toshinobu Machida1, Hidekazu Matsueda2,b, Taku Umezawa1, Akihiko Ito1, Shin-Ichiro Nakaoka1, Hiroshi Tanimoto1, and Yasunori Tohjima1 Yosuke Niwa et al.
  • 1National Institute for Environmental Studies, Tsukuba, Japan
  • 2Meteorological Research Institute, Tsukuba, Japan
  • anow at: Japan Meteorological Agency, Tokyo, Japan
  • bnow at: Dokkyo University, Soka, Japan

Abstract. The inverse analysis was used to estimate the fire carbon emission in Equatorial Asia induced by the big El Niño in 2015. This inverse analysis is unique because it extensively used high-precision atmospheric mole fraction data of carbon dioxide (CO2) from the commercial aircraft observation project. By comparisons with independent shipboard observations, especially carbon monoxide (CO) data, the validity of the estimated fire-induced carbon emission was elucidated. The best estimate, which used both aircraft and shipboard CO2 observations, indicated 273 Tg C for fire emission during September–October 2015. This two-month-long emission accounts for 75 % of the annual total fire emission and 45 % of the annual total net carbon flux within the region, indicating that fire emission is a dominant driving force of interannual variations of carbon fluxes in Equatorial Asia. Several sensitivity experiments demonstrated that aircraft observations could measure fire signals, though they showed a certain degree of sensitivity to prior fire-emission data. The inversions coherently estimated smaller fire emissions than the priors, partially because of the small contribution of peatland fires, indicated by enhancement ratios of CO and CO2 observed by the ship. In the future warmer climate condition, Equatorial Asia would experience more severe droughts and have risks for releasing a large amount of carbon into the atmosphere. Therefore, the continuation of aircraft and shipboard observations is fruitful for reliable monitoring of carbon fluxes in Equatorial Asia.

Yosuke Niwa et al.

 
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Yosuke Niwa et al.

Yosuke Niwa et al.

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Short summary
Fires in Equatorial Asia release a large amount of carbon into the atmosphere. Extensively using high-precision atmospheric data of carbon dioxide (CO2) from a commercial aircraft observation project, we estimated the fire carbon emission in Equatorial Asia induced by the big El Niño in 2015. Additional shipboard measurement data elucidated the validity of the analysis and the best estimate indicated 273 Tg C for fire emission during September–October 2015.
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