Precision requirements for space‐based data

Abstract

[1] Precision requirements are determined for space-based column-averaged CO 2 dry air mole fraction (X CO 2 ) data. These requirements result from an assessment of spatial and temporal gradients in X CO 2 , the relationship between X CO 2 precision and surface CO 2 flux uncertainties inferred from inversions of the X CO 2 data, and the effects of X CO 2 biases on the fidelity of CO 2 flux inversions. Observational system simulation experiments and synthesis inversion modeling demonstrate that the Orbiting Carbon Observatory mission design and sampling strategy provide the means to achieve these X CO 2 data precision requirements.

The Total Carbon Column Observing Network

“…NDACC). In fact, the precision requirement on the TCCON X CO 2 is likely to be stricter than for satellite instruments such as the Orbiting Carbon Observatory, which is calculated to be approximately 0.25 per cent (less than 1 ppm) for global monthly means [15]. This is because of the reduced spatial density of the TCCON observations, and because the TCCON measurements must be more precise and accurate than the satellite measurements if they are to provide a useful validation dataset.…”

The air-broadened, near-infrared CO2 line shape in the spectrally isolated regime: Evidence of simultaneous Dicke narrowing and speed dependence

“…3 Of particular importance are higher order effects such as collisional narrowing, speeddependent effects and line mixing which are yet to be incorporated into the vast majority of atmospheric retrievals which often employ the Voigt line profile. These effects will play an even greater role in next generation, active sensing missions [4][5][6][7][8][9][10][11] (including NASA's Active Sensing of CO 2 Emissions over Nights Days and Seasons, ASCENDS) where individual transitions in the near-infrared spectral region will be interrogated rather than entire bands, and where precise measurements of CO 2 concentrations will require exquisite knowledge of the spectral line shape.…”

“…1,2 These applications will require a detailed and thorough understanding of the near-infrared spectral line shapes of CO 2 and O 2 over the range of atmospherically relevant temperatures and pressures. 3 Of particular importance are higher order effects such as collisional narrowing, speeddependent effects and line mixing which are yet to be incorporated into the vast majority of atmospheric retrievals which often employ the Voigt line profile.…”

SCIAMACHY WFM-DOAS <i>X</i>CO<sub>2</sub>: reduction of scattering related errors

“…Satellite observations of the column-averaged dry air mole fractions of CO 2 (denoted XCO 2 ) can close these gaps (Rayner and O'Brien, 2001;Houweling et al, 2004;Miller et al, 2007;Chevallier et al, 2007). This, however, requires a high accuracy and precision of the XCO 2 data product to constrain the surface fluxes of CO 2 significantly (Chevallier et al, 2007;Miller et al, 2007).…”