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|Title:||Quantification of uncertainties in OCO-2 measurements of XCO<inf>2</inf>: Simulations and linear error analysis|
Payne, V. H.
|Publisher:||European Geosciences Union (EGU), Copernicus Publications|
|Citation:||Atmospheric Measurement Techniques, 2016, 9 (10), pp. 5227-5238|
|Abstract:||We present an analysis of uncertainties in global measurements of the column averaged dry-air mole fraction of CO2 (XCO2) by the NASA Orbiting Carbon Observatory-2 (OCO-2). The analysis is based on our best estimates for uncertainties in the OCO-2 operational algorithm and its inputs, and uses simulated spectra calculated for the actual flight and sounding geometry, with measured atmospheric analyses. The simulations are calculated for land nadir and ocean glint observations. We include errors in measurement, smoothing, interference, and forward model parameters. All types of error are combined to estimate the uncertainty in XCO2 from single soundings, before any attempt at bias correction has been made. From these results we also estimate the "variable error" which differs between soundings, to infer the error in the difference of XCO2 between any two soundings. The most important error sources are aerosol interference, spectroscopy, and instrument calibration. Aerosol is the largest source of variable error. Spectroscopy and calibration, although they are themselves fixed error sources, also produce important variable errors in XCO2. Net variable errors are usually <1 ppm over ocean and ∼ 0.5-2.0 ppm over land. The total error due to all sources is ∼ 1.5-3.5ppm over land and ∼ 1.5-2.5 ppm over ocean.|
|Rights:||© Author(s) 2016. This work is distributed under the Creative Commons Attribution 3.0 License.|
|Description:||The simulations and analyses reported in this paper are not a part of the OCO-2 data set or of the public record of the OCO-2 project. They are exploratory in nature and not publically accessible because it has not been feasible to select, catalog, and document the relevant material. The Supplement related to this article is available online at doi:10.5194/amt-9-5227-2016-supplement.|
|Appears in Collections:||Published Articles, Dept. of Physics and Astronomy|
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