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Improved Constraints on Northern Extratropical CO 2 Fluxes Obtained by Combining Surface‐Based and Space‐Based Atmospheric CO 2 Measurements
Author(s) -
Byrne B.,
Liu J.,
Lee M.,
Baker I.,
Bowman K. W.,
Deutscher N. M.,
Feist D. G.,
Griffith D. W. T.,
Iraci L. T.,
Kiel M.,
Kimball J. S.,
Miller C. E.,
Morino I.,
Parazoo N. C.,
Petri C.,
Roehl C. M.,
Sha M. K.,
Strong K.,
Velazco V. A.,
Wennberg P. O.,
Wunch D.
Publication year - 2020
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2019jd032029
Subject(s) - flux (metallurgy) , environmental science , atmospheric sciences , greenhouse gas , inversion (geology) , sampling (signal processing) , consistency (knowledge bases) , meteorology , mathematics , geology , chemistry , physics , paleontology , oceanography , organic chemistry , structural basin , detector , optics , geometry
Top‐down estimates of CO 2 fluxes are typically constrained by either surface‐based or space‐based CO 2 observations. Both of these measurement types have spatial and temporal gaps in observational coverage that can lead to differences in inferred fluxes. Assimilating both surface‐based and space‐based measurements concurrently in a flux inversion framework improves observational coverage and reduces sampling related artifacts. This study examines the consistency of flux constraints provided by these different observations and the potential to combine them by performing a series of 6‐year (2010–2015) CO 2 flux inversions. Flux inversions are performed assimilating surface‐based measurements from the in situ and flask network, measurements from the Total Carbon Column Observing Network (TCCON), and space‐based measurements from the Greenhouse Gases Observing Satellite (GOSAT), or all three data sets combined. Combining the data sets results in more precise flux estimates for subcontinental regions relative to any of the data sets alone. Combining the data sets also improves the accuracy of the posterior fluxes, based on reduced root‐mean‐square differences between posterior flux‐simulated CO 2 and aircraft‐based CO 2 over midlatitude regions (0.33–0.56 ppm) in comparison to GOSAT (0.37–0.61 ppm), TCCON (0.50–0.68 ppm), or in situ and flask measurements (0.46–0.56 ppm) alone. These results suggest that surface‐based and GOSAT measurements give complementary constraints on CO 2 fluxes in the northern extratropics and can be combined in flux inversions to improve constraints on regional fluxes. This stands in contrast with many earlier attempts to combine these data sets and suggests that improvements in the NASA Atmospheric CO 2 Observations from Space (ACOS) retrieval algorithm have significantly improved the consistency of space‐based and surface‐based flux constraints.