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CO 2 transport uncertainties from the uncertainties in meteorological fields
Author(s) -
Liu Junjie,
Fung Inez,
Kalnay Eugenia,
Kang JiSun
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl047213
Subject(s) - environmental science , meteorology , advection , atmosphere (unit) , sensible heat , atmospheric sciences , flux (metallurgy) , climatology , geology , geography , physics , materials science , metallurgy , thermodynamics
Inference of surface CO 2 fluxes from atmospheric CO 2 observations requires information about large‐scale transport and turbulent mixing in the atmosphere, so transport errors and the statistics of the transport errors have significant impact on surface CO 2 flux estimation. In this paper, we assimilate raw meteorological observations every 6 hours into a general circulation model with a prognostic carbon cycle (CAM3.5) using the Local Ensemble Transform Kalman Filter (LETKF) to produce an ensemble of meteorological analyses that represent the best approximation to the atmospheric circulation and its uncertainty. We quantify CO 2 transport uncertainties resulting from the uncertainties in meteorological fields by running CO 2 ensemble forecasts within the LETKF‐CAM3.5 system forced by prescribed surface fluxes. We show that CO 2 transport uncertainties are largest over the tropical land and the areas with large fossil fuel emissions, and are between 1.2 and 3.5 ppm at the surface and between 0.8 and 1.8 ppm in the column‐integrated CO 2 (with OCO‐2‐like averaging kernel) over these regions. We further show that the current practice of using a single meteorological field to transport CO 2 has weaker vertical mixing and stronger CO 2 vertical gradient when compared to the mean of the ensemble CO 2 forecasts initialized by the ensemble meteorological fields, especially over land areas. The magnitude of the difference at the surface can be up to 1.5 ppm.