A decadal inversion of CO2 using the Global Eulerian-Lagrangian Coupled Atmospheric model (GELCA): sensitivity to the ground-based observation network

We present an assimilation system for atmospheric carbon dioxide (CO 2 ) using a Global Eulerian-Lagrangian Coupled Atmospheric model (GELCA), and demonstrate its capability to capture the observed atmospheric CO 2 mixing ratios and to estimate CO 2 fluxes. With the efficient data handling scheme in...

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Bibliographic Details
Published in:Tellus. Series B, Chemical and physical meteorology Chemical and physical meteorology, 2017-01, Vol.69 (1), p.1291158
Main Authors: Shirai, T., Ishizawa, M., Zhuravlev, R., Ganshin, A., Belikov, D., Saito, M., Oda, T., Valsala, V., Gomez-Pelaez, A.J., Langenfelds, R., Maksyutov, S.
Format: Article
Language:English
Subjects:
Airborne observation
Aircraft
Aircraft observations
Assimilation
Atmospheric models
carbon cycle
Carbon dioxide
Carbon dioxide atmospheric concentrations
Carbon dioxide flux
coupled model
Data
Data analysis
flux estimation
Fluxes
Ground-based observation
Growth rate
Inversion
Mixing ratio
Regional analysis
Seasonal variation
Sensitivity
Surface fluxes
top-down approach
tropical Asia
Tropical climate
Tropical environments
Uncertainty
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Summary:We present an assimilation system for atmospheric carbon dioxide (CO 2 ) using a Global Eulerian-Lagrangian Coupled Atmospheric model (GELCA), and demonstrate its capability to capture the observed atmospheric CO 2 mixing ratios and to estimate CO 2 fluxes. With the efficient data handling scheme in GELCA, our system assimilates non-smoothed CO 2 data from observational data products such as the Observation Package (ObsPack) data products as constraints on surface fluxes. We conducted sensitivity tests to examine the impact of the site selections and the prior uncertainty settings of observation on the inversion results. For these sensitivity tests, we made five different site/data selections from the ObsPack product. In all cases, the time series of the global net CO 2 flux to the atmosphere stayed close to values calculated from the growth rate of the observed global mean atmospheric CO 2 mixing ratio. At regional scales, estimated seasonal CO 2 fluxes were altered, depending on the CO 2 data selected for assimilation. Uncertainty reductions were determined at the regional scale and compared among cases. As measures of the model-data mismatch, we used the model-data bias, root-mean-square error, and the linear correlation. For most observation sites, the model-data mismatch was reasonably small. Regarding regional flux estimates, tropical Asia was one of the regions that showed a significant impact from the observation network settings. We found that the surface fluxes in tropical Asia were the most sensitive to the use of aircraft measurements over the Pacific, and the seasonal cycle agreed better with the results of bottom-up studies when the aircraft measurements were assimilated. These results confirm the importance of these aircraft observations, especially for constraining surface fluxes in the tropics.
ISSN:0280-6509
1600-0889
DOI:10.1080/16000889.2017.1291158