Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 9 2009 10.5194/acp-9-3043-2009 http://www.atmos-chem-phys.net/9/3043/2009/ http://www.atmos-chem-phys.net/9/3043/2009/acp-9-3043-2009.html http://www.atmos-chem-phys.net/9/3043/2009/acp-9-3043-2009.pdf 3043 3048 2009-05-12 Assessing temporal clear-sky errors in assimilation of satellite CO₂ retrievals using a global transport model K. D. Corbin kdcorbin@atmos.colostate.edu A. S. Denning N. C. Parazoo Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA The Orbiting Carbon Observatory (OCO) and the Greenhouse gases Observing SATellite (GOSAT) will make global observations of the total column dry-air mole fraction of atmospheric CO₂ (<i>X</i>_CO₂) starting in 2008. Although satellites have global coverage, <i>X</i>_CO₂ retrievals will be made only a few times each month over a given location and will only be sampled in clear conditions. Modelers will use <i>X</i>_CO₂ in atmospheric inversions to estimate carbon sources and sinks; however, if satellite measurements are used to represent temporal averages, modelers may incur temporal sampling errors. We investigate these errors using a global transport model. Temporal sampling errors vary with time and location, exhibit spatially coherent patterns, and are greatest over land and during summer. These errors often exceed 1 ppm and must be addressed in a data assimilation system by correct simulation of synoptic CO₂ variations associated with cloud systems. Andres, R. J., Marland, G., Fung, I., and Matthews, E.: A 1$^\circ\times1^\circ$ distribution of carbon dioxide emissions from fossil fuel \mboxconsumption and cement manufacture, 1950–1990, Global Biogeochem. Cy., 10(3), 419–430, 1996. Baker, I. T., Denning, A. S., Prihodko, L., Schaefer, K., Berry, J. A., Collatz, G. J., Suits, N. 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