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Volume 18, issue 20
Atmos. Chem. Phys., 18, 14851-14866, 2018
https://doi.org/10.5194/acp-18-14851-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: The 10th International Carbon Dioxide Conference (ICDC10)...

Atmos. Chem. Phys., 18, 14851-14866, 2018
https://doi.org/10.5194/acp-18-14851-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 17 Oct 2018

Research article | 17 Oct 2018

Seasonal evaluation of tropospheric CO2 over the Asia-Pacific region observed by the CONTRAIL commercial airliner measurements

Taku Umezawa1, Hidekazu Matsueda2, Yousuke Sawa2, Yosuke Niwa2,a, Toshinobu Machida1, and Lingxi Zhou3 Taku Umezawa et al.
  • 1National Institute for Environmental Studies, Tsukuba, Japan
  • 2Meteorological Research Institute, Tsukuba, Japan
  • 3Chinese Academy of Meteorological Sciences, Beijing, China
  • anow at: National Institute for Environmental Studies, Tsukuba, Japan

Abstract. Measurement of atmospheric carbon dioxide (CO2) is indispensable for top-down estimation of surface CO2 sources/sinks by an atmospheric transport model. Despite the growing importance of Asia in the global carbon budget, the region has only been sparsely monitored for atmospheric CO2 and our understanding of atmospheric CO2 variations in the region (and thereby that of the regional carbon budget) is still limited. In this study, we present climatological CO2 distributions over the Asia-Pacific region obtained from the CONTRAIL (Comprehensive Observation Network for TRace gases by AIrLiner) measurements. The high-frequency in-flight CO2 measurements over 10 years reveal a clear seasonal variation in CO2 in the upper troposphere (UT), with a maximum occurring in April–May and a minimum in August–September. The CO2 mole fraction in the UT north of 40°N is low and highly variable in June–August due to the arrival of air parcels with seasonally low CO2 caused by the summertime biospheric uptake in boreal Eurasia. For August–September in particular, the UT CO2 is noticeably low within the Asian summer monsoon anticyclone associated with the convective transport of strong biospheric CO2 uptake signal over South Asia. During September as the anticyclone decays, a spreading of this low-CO2 area in the UT is observed in the vertical profiles of CO2 over the Pacific Rim of continental East Asia. Simulation results identify the influence of anthropogenic and biospheric CO2 fluxes in the seasonal evolution of the spatial CO2 distribution over the Asia-Pacific region. It is inferred that a substantial contribution to the UT CO2 over the northwestern Pacific comes from continental East Asian emissions in spring; but in the summer monsoon season, the prominent air mass origin switches to South Asia and/or Southeast Asia with a distinct imprint of the biospheric CO2 uptake. The CONTRAIL CO2 data provide useful constraints to model estimates of surface fluxes and to the evaluation of the satellite observations, in particular for the Asia-Pacific region.

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Distribution of atmospheric CO2 is key to estimate surface CO2 sources and sinks. We present extensive analysis of a unique 10-year three-dimensional dataset of atmospheric CO2 achieved by the CONTRAIL commercial airliner measurements over the Asia-Pacific region. Aided by model simulations, we identified the influence of anthropogenic and biospheric CO2 fluxes in the seasonal evolution of the spatial CO2 distributions under the seasonally varying meteorology (e.g., Asian summer monsoon)
Distribution of atmospheric CO2 is key to estimate surface CO2 sources and sinks. We present...
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