The Orbiting Carbon Observatory-2: First 18 months of Science Data Products

Abstract

Abstract. The Orbiting Carbon Observatory-2 (OCO-2) is the first National Aeronautics and Space Administration (NASA) satellite designed to measure atmospheric carbon dioxide (CO2) with the accuracy, resolution, and coverage needed to quantify CO2 fluxes (sources and sinks) on regional scales. OCO-2 was successfully launched on 2 July 2014, and joined the 705 km Afternoon Constellation on 3 August 2014. On monthly time scales, 7 to 12 % of these measurements are sufficiently cloud and aerosol free to yield estimates of the column-averaged atmospheric CO2 dry air mole fraction, XCO2, that pass all quality tests. During the first year of operations, the observing strategy, instrument calibration, and retrieval algorithm were optimized to improve both the data yield and the accuracy of the products. With these changes, global maps of XCO2 derived from the OCO-2 data are revealing some of the most robust features of the atmospheric carbon cycle. This includes XCO2 enhancements co-located with intense fossil fuel emissions in eastern US and eastern China, which are most obvious between October and December, when the north-south XCO2 gradient is small. Enhanced XCO2 coincident with biomass burning in the Amazon, central Africa, and Indonesia is also evident in this season. In May and June, when the north-south XCO2 gradient is largest, these sources are less apparent in global maps. During this part of the year, OCO-2 maps show a more than 10 ppm reduction in XCO2 across the northern hemisphere, as photosynthesis by the land biosphere rapidly absorbs CO2. As the carbon cycle science community continues to analyze these OCO-2 data, information on regional-scale sources (emitters) and sinks (absorbers) which impart XCO2 changes on the order of 1 ppm, as well as far more subtle features, will emerge from this high resolution, global data set.

Quantifying the Impact of Atmospheric Transport Uncertainty on CO2 Surface Flux Estimates

“…The OCO-2 satellite was launched in July 2014, with the goal of estimating atmospheric CO 2 mole fractions from spectroscopic absorption features of CO 2 and O 2 in the near-infrared spectrum (Eldering et al, 2017). The most constrained feature of CO 2 in a given sounding is the pressure-weighted column average or X CO 2 .…”

The Cross-Calibration of Spectral Radiances and Cross-Validation of CO2 Estimates from GOSAT and OCO-2

“…About 30% of matched-up XCO 2 data were screened out with this criterion. Crisp et al [10] and Eldering et al [20] describe the OCO-2 instrument performance and radiometrically calibrated products and retrieved XCO 2 . In general, the OCO-2 instrument performed as expected during its first 18 months.…”

A Fast Atmospheric Trace Gas Retrieval for Hyperspectral Instruments Approximating Multiple Scattering—Part 2: Application to XCO2 Retrievals from OCO-2

“…As can be seen, the large scale pattern of the total bias is dominated by the land/sea bias followed by the footprint bias and the linear bias model plays only a minor role. For comparison, Figure 12 (right) shows the total bias pattern of NASA's operational OCO-2 L2 product v7.3.05b [21,22] obtained from https://daac.gsfc.nasa.gov and in the following referred to as NASA v7.3.05b. The overall variability is similar (0.82 ppm and 0.71 ppm for FOCAL v06 and NASA v7.3.05b, respectively) and the NASA product also has a distinct land/sea bias but with opposite sign, i.e., with largest values over sea (note the reversed color bar in Figure 12, right).…”

“…Because of the sparse ground based validation sites, the analyses of an ensemble of independently developed algorithms can give important insights in the quality of the retrievals, especially, remote from the validation sites [19] and strengthen the geophysical interpretation of the data [20]. Nevertheless, so far only the operational NASA algorithm exists for OCO-2 [21,22] covering the whole mission period.…”