Error correlation between CO2 and CO as constraint for CO2 flux inversions using satellite data
Item
Title (Dublin Core)
Error correlation between CO2 and CO as constraint for CO2 flux inversions using satellite data
Description (Dublin Core)
Inverse modeling of CO<sub>2</sub> satellite observations to better quantify carbon surface fluxes requires a chemical transport model (CTM) to relate the fluxes to the observed column concentrations. CTM transport error is a major source of uncertainty. We show that its effect can be reduced by using CO satellite observations as additional constraint in a joint CO<sub>2</sub>-CO inversion. CO is measured from space with high precision, is strongly correlated with CO<sub>2</sub>, and is more sensitive than CO<sub>2</sub> to CTM transport errors on synoptic and smaller scales. Exploiting this constraint requires statistics for the CTM transport error correlation between CO<sub>2</sub> and CO, which is significantly different from the correlation between the concentrations themselves. We estimate the error correlation globally and for different seasons by a paired-model method (comparing GEOS-Chem CTM simulations of CO<sub>2</sub> and CO columns using different assimilated meteorological data sets for the same meteorological year) and a paired-forecast method (comparing 48- vs. 24-h GEOS-5 CTM forecasts of CO<sub>2</sub> and CO columns for the same forecast time). We find strong error correlations (<i>r</i><sup>2</sup>>0.5) between CO<sub>2</sub> and CO columns over much of the extra-tropical Northern Hemisphere throughout the year, and strong consistency between different methods to estimate the error correlation. Application of the averaging kernels used in the retrieval for thermal IR CO measurements weakens the correlation coefficients by 15% on average (mostly due to variability in the averaging kernels) but preserves the large-scale correlation structure. We present a simple inverse modeling application to demonstrate that CO<sub>2</sub>-CO error correlations can indeed significantly reduce uncertainty on surface carbon fluxes in a joint CO<sub>2</sub>-CO inversion vs. a CO<sub>2</sub>-only inversion.
Creator (Dublin Core)
Wang, H.
Jacob, D. J.
Kopacz, M.
Jones, D. B. A.
Suntharalingam, P.
Fisher, J. A.
Nassar, R.
Pawson, S.
Nielsen, J. E.
Date (Dublin Core)
2018-01-15
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-9-7313-2009
https://acp.copernicus.org/articles/9/7313/2009/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
