|Name||NASA Jet Propulsion Laboratory, California Institute of Technology|
|Address 2||4800 Oak Grove Drive|
|Address 3||Pasadena, CA 91109|
|Country/Territory||United States of America|
|Organization name||NASA Jet Propulsion Laboratory, California Institute of Technology|
|Organization country/territory||United States of America|
|Address 1||MS 233-200|
|Address 2||4800 Oak Grove Drive|
|Address 3||Pasadena, CA 91101|
|Country/territory||United States of America|
|Last updated date||2022-05-11|
9999-12-31 00:00:00 - 9999-12-31 23:59:59: OCO-2 spectrometer(3-channel imaging grating spectrometer)
Both internationally-recognized validation standards and validation protocols have been established to identify and characterize biases in the OCO-2 XCO2 product. The ground-based and aircraft-based in situ CO2 measurements available through the World Meteorological Organization (WMO) Global Atmospheric Watch (GAW) program have been adopted as the reference standard. These measurements play a critical role OCO-2 XCO2 validation, but cannot be used directly because they describe the concentrations of CO2 at a single surface station or along a horizontal or vertical flight path, while the space-based XCO2 estimates refer to a vertically integrated atmospheric optical path that extends from the top of the atmosphere to the surface and back to the spacecraft. The ground-based XCO2 estimates retrieved from the measurements collected by the Total Carbon Column Observing Network (TCCON) Fourier Transform Spectrometer (FTS) instruments provide a transfer standard between the space-based XCO2 estimates and the WMO GAW standards.
Each TCCON station incorporates an FTS with a solar tracker to acquire high-resolution (< 0.02 cm-1) spectra of direct sunlight from the center ∼10% of the solar disk (Wunch et al., 2011). Because the TCCON FTS instruments measure a bright target at very high spectral resolution, their measurements have much greater sensitivity to CO2 variations than the observations of reflected sunlight collected by the OCO-2 spectrometers. In additional, TCCON XCO2 estimates have much smaller biases contributed by uncertainties in the atmospheric optical path length than those from OCO-2 because most of the light that they measure travels directly from the solar disk while OCO-2 measures sunlight that has been scattered by the surface and atmosphere, traversing a range of optical paths. In early 2021, there were ∼27 TCCON instruments operating at latitudes between Eureka, Canada (80.05°N) and Lauder, New Zealand (45.038°S).
The data collected by these stations are analyzed to yield high precision estimates of XCO2 and several other trace species (CH4, N2O, HF, CO, H2O, and HDO). To relate these estimates to the WMO GAW standard scales, in situ vertical profiles of CO2 and other species above the stations are measured using in situ sensors on fixed-wing aircraft (Washenfelder et al., 2006; Messerschmidt et al., 2011; Wofsy et al., 2011) and AirCore sensors on high-altitude balloons (Karion et al., 2010). The TCCON team combines aircraft and AirCore profiles with climatological upper atmosphere data and integrates over the atmospheric column to estimate XCO2. These estimates are compared to XCO2 and estimates retrieved from simultaneous TCCON measurements. A global bias correction is then applied to the TCCON estimates to reconcile any differences between the TCCON and the in situ standard (Wunch et al., 2015).
To validate the OCO-2 XCO2 estimates against those from TCCON, values retrieved from the satellite measurements collected near a TCCON station are compared to those retrieved from the simultaneous up-looking measurements from that TCCON station. OCO-2 routinely acquires observations near TCCON stations while pointing to the local nadir or near the apparent “glint spot”, where sunlight is reflected specularly from the surface. It can also target TCCON station as it flies overhead, collecting hundreds or thousands of coincident measurements on a single overpass. OCO-2 nadir, glint and target observations near TCCON sites are used to validate the OCO-2 products (Wunch et al., 2017; Kiel et al., 2019). These comparisons have yielded valuable insights into the surface and atmospheric properties that contribute to biases and scatter in the OCO-2 XCO2 products (c.f. O’Dell et al. 2018; Kiel et al. 2019). These insights have facilitated the development and application of bias correction algorithms that have further improved the product. By applying simple parametric bias corrections, the agreement between OCO-2 and TCCON XCO2 estimates is now better than 1 ppm (Wunch et al., 2017; O’Dell et al., 2018) across the TCCON network.
For more information, please refer to Data Product User’s Guide https://docserver.gesdisc.eosdis.nasa.gov/public/project/OCO/OCO2_OCO3_B10_DUG.pdf
Science and housekeeping data from OCO-2 are transmitted to a NASA Near Earth Network station in Alaska or the Troll Satellite Station in Antarctica twice each day. The data are then transferred to the Earth Science Mission Operations center at the NASA Goddard Space Flight Center (GSFC), where the raw telemetry is converted to time-ordered raw radiance spectra (Level 0 Products). The Level 0 products are then delivered to the OCO-2 Science Data Operations System at the NASA Jet Propulsion Laboratory (JPL), where full orbit "granules" are first processed to yield radiometrically-calibrated geolocated spectral radiances within the O2 and CO2 bands (Level 1b Products). The boresighted spectra for each coincident CO2/O2 sounding are then processed to estimate the column-averaged CO2 dry air mole fraction, XCO2 (L2 Products).
For more information, please refer to ALGORITHM THEORETICAL BASIS DOCUMENT https://docserver.gesdisc.eosdis.nasa.gov/public/project/OCO/OCO_L1B_ATBD.pdf
Original Data Version: OCO-2 Level 2 bias-corrected XCO2 and other select fields from the full-physics retrieval aggregated as daily files, Retrospective processing V10r
Foot print of OCO-2 spectrometers at nadir: < 1.29 km by 2.25 km
To cite the data in publications: OCO-2 Science Team/Michael Gunson, Annmarie Eldering (2020), OCO-2 Level 2 bias-corrected XCO2 and other select fields from the full-physics retrieval aggregated as daily files, Retrospective processing V10r, Greenbelt, MD, USA, Goddard Earth Sciences Data and Information Services Center (GES DISC), Accessed: 2022-05-11, 10.5067/E4E140XDMPO2
The OCO-2 Data Product:
The Orbiting Carbon Observatory-2 (OCO-2) carries and points a three-channel imaging grating spectrometer that collects high-resolution, co-boresighted spectra of reflected sunlight within the molecular oxygen (O2) A-band at 0.765 microns (μm) and the weak and strong CO2 bands at 1.61 and 2.06 μm (Crisp et al. 2017). Spectra are recorded in eight contiguous spatial footprints across a narrow (< 0.8°) field of view (FOV) at 1/3 second intervals, yielding 24 soundings per second with footprints areas < 3 km2 along a narrow (< 10 km wide) ground track. Co-boresighted spectra from the three channels are combined to form soundings, which are analyzed with a state-of-the-art, physics-based, remote sensing retrieval algorithm to yield spatially resolved estimates of XCO2 (Eldering et al. 2017; O´Dell et al. 2018).
For routine science operations, OCO-2 points the spectrometer´s FOV at the local nadir or near the "glint spot," where sunlight is specularly reflected from the surface. Nadir observations yield higher spatial resolution over land, while glint measurements have greater sensitivity over ocean. Each month, OCO-2 returns ∼2.5 million soundings that are sufficiently cloud-free to yield full-column estimates of XCO2 with single-sounding precisions near 0.5ppm and accuracies <1 ppm at solar zenith angles as large as 70° (Eldering et al. 2017; Wunch et al., 2017).
In addition to XCO2, OCO-2 returns precise measurements of solar-induced chlorophyll fluorescence (SIF). SIF must be quantified and corrected in the O2 A-band channel to ensure accurate estimates of XCO2 (Frankenberg et al. 2012, 2011a). SIF is also a functional proxy for terrestrial gross primary productivity (GPP; Frankenberg et al. 2011b; Guanter et al. 2012; Joiner et al. 2013; Köhler et al. 2015; Sun et al. 2017; 2018; Magney et al. 2019). SIF-based estimates of GPP are being combined with XCO2 in atmospheric inverse models to provide new constraints on CO2 uptake by the land biosphere and new insights into carbon-climate feedbacks (Liu et al. 2017; Palmer et al. 2019).
|1||OCO-2 Project website: https://ocov2.jpl.nasa.gov/|
|2||Data Product User’s Guide https://docserver.gesdisc.eosdis.nasa.gov/public/project/OCO/OCO2_OCO3_B10_DUG.pdf|
|3||Frankenberg, C., Fisher, J. B., Worden, J., Badgley, G., Saatchi, S. S., Lee, J.-F., Toon, G. C., Butz, A., Jung, M., Kuze, A., and Yokota, T., (2011b), New global observations of the terrestrial carbon cycle from GOSAT: Patterns of plant fluorescence with gross primary productivity, Geophys. Res. Lett., 38, L17706, doi:10.1029/2011GL048738.|
|4||ORBITING CARBON OBSERVATORY (OCO) - 2 LEVEL 2 FULL PHYSICS ALGORITHM Theoretical Basis Document https://docserver.gesdisc.eosdis.nasa.gov/public/project/OCO/OCO_L2_ATBD.pdf|
|5||Guanter, L., et al., (2012), Retrieval and global assessment of terrestrial chlorophyll fluorescence from GOSAT space measurements, Remote Sensing of Environment, 121: 236–251.|
|6||Eldering, A., O’Dell, C. W., Wennberg, P. O., Crisp, D., Gunson, M.R., Viatte, C., Avis, C., Braverman, A., Bruegge, Castano, C., R., Chang, A., Chapsky, L., Cheng, C., Connor, B., Dan, L., Doran, G., Fisher, B., Frankenberg, C., Fu, D., Granat, R., Hobbs, J., Lee, R.A.M., Mandrake, L., McDuffie ,J., Miller, C.E., Myers, V., Natraj, V., O’Brien, D., Osterman, G., Oyafuso, F., Payne, V., Pollock, H. R., Polonsky, I., Roehl, C., Rosenberg, R., Schwandner, F., Smyth, M., Tang, V., Taylor, T., To, C., Wunch, D., and Yoshimizu, J., (2017), The Orbiting Carbon Observatory-2: First 18 months of Science Data Products, Atmos. Meas. Tech., 10: 549–563, doi:10.5194/amt-10-549-2017.|
|7||Kiel, M., O’Dell, C. W., Fisher, B., et al., (2019), How bias correction goes wrong: measurement of X-CO2 affected by erroneous surface pressure estimates, Atmospheric Measurement Techniques, 12(4): 2241–2259, doi: 10.5194/amt-12-2241-2019.|
|8||Sun, Y., Frankenberg, C., Jung, M., et al., (2018), Overview of solar-induced chlorophyll fluorescence (SIF) from the Orbiting Carbon Observatory-2: Retrieval, cross-mission comparison, and global monitoring for GPP, Remote Sensing of Environment, 209, 808–823.|
|9||Wunch, D., Toon, G. C., Blavier, J.-F. L., Washenfelder, R. A., Notholt, J., Connor, B. J., Griffith, D. W., Sherlock, V., and Wennberg, P. O., (2011), The total carbon column observing network, Philos. T. R. Soc. A, 369, 2087–2112, doi:10.1098/rsta.2010.0240.|
|10||Wunch, D., Wennberg, P. O., Osterman, G., Fisher, B., Naylor, B., Roehl, C. M., O’Dell, C., Mandrake, L., Viatte, C., Griffith, D. W., Deutscher, N. M., Velazco, V. A., Notholt, J., Warneke, T., Petri, C., De Maziere, M., Sha, M. K., Sussmann, R., Rettinger, M., Pollard, D., Robinson, J., Morino, I., Uchino, O., Hase, F., Blumenstock, T., Kiel, M., Feist, D. G., Arnold, S. G., Strong, K., Mendonca, J., Kivi, R., Heikkinen, P., Iraci, L., Podolske, J., Hillyard, P. W., Kawakami, S., Dubey, M. K., Parker, H. A., Sepulveda, E., Rodriguez, O. E. G., Te, Y., Jeseck, P., Gunson, M. R., Crisp, D., and Eldering, A., (2017), Comparisons of the Orbiting Carbon Observatory-2 (OCO-2) XCO2 measurements with TCCON, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-227.|
|11||Messerschmidt, J., Geibel, M. C., Blumenstock, T., Chen, H., Deutscher, N. M., Engel, A., Feist, D. G., Gerbig, C., Gisi, M., Hase, F., Katrynski, K., Kolle, O., Lavrič, J. V., Notholt, J., Palm, M., Ramonet, M., Rettinger, M., Schmidt, M., Sussmann, R., Toon, G. C., Truong, F., Warneke, T., Wennberg, P. O., Wunch, D., and Xueref-Remy, I., (2011), Calibration of TCCON column-averaged CO2: the first aircraft campaign over European TCCON sites, Atmos. Chem. Phys., 11, 10765-10777, doi:10.5194/acp-11-10765-2011.|
|12||Wofsy, S. C., B. Daube, R. Jimenez, E. Kort, J. V. Pittman, S. Park, R. Commane, B. Xiang, G. Santoni, D. Jacob, J. Fisher, C. Pickett-Heaps, H. Wang, K. J. Wecht, Q.-Q. Wang, B. B. Stephens, S. Shertz, P. Romashkin, T. Campos, J. Haggerty, W. A. Cooper, D. Rogers, S. Beaton, R. Hendershot, J. W. Elkins, D. Fahey, R. Gao, F. Moore, S. A. Montzka, J. Schwarz, D. Hurst, B. Miller, C. Sweeney, S. Oltmans, D. Nance, E. Hintsa, G. Dutton, L. Watts, R. Spackman, K. Rosenlof, E. Ray, M. A. Zondlo, M. Diao, R. Keeling, J. Bent, E. Atlas, R. Lueb, M. J. Mahoney, M. Chahine, E. Olson, P. Patra, K. Ishijima, R. Engelen, J. Flemming, R. Nassar, D. B. A. Jones, and S. E. M. Fletcher, (2011), HIAPER Pole-to-Pole Observations (HIPPO): Fine-grained, global scale measurements of climatically important atmospheric gases and aerosols, Philosophical Transactions of the Royal Society of London A, 369, 2073-2086, doi:10.1098/rsta.2010.0313.|
|13||Wunch, D., Toon, G. C., Sherlock, V., Deutscher, N. M., Liu, C., Feist, D. G., and Wennberg, P. O., (2015), The Total Carbon Column Observing Network’s GGG2014 Data Version, Tech. rep., California Institute of Technology, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA, https://doi.org/10.14291/tccon.ggg2014.documentation.R0/1221662.|
|14||Crisp, D., Pollock, H. R., Rosenberg, R., Chapsky, L., Lee, R. A. M., Oyafuso, F. A., Frankenberg, C., O’Dell, C. W., Bruegge, C. J., Doran, G. B., Eldering, A., Fisher, B. M., Fu, D., Gunson, M. R., Mandrake, L., Osterman, G. B., Schwandner, F. M., Sun, K., Taylor, T. E., Wennberg, P. O., and Wunch, D., (2017), The On-Orbit Performance of the Orbiting Carbon Observatory-2 (OCO-2) Instrument and its Radiometrically Calibrated Products, Atmos. Meas. Tech. 10, 59-81, doi:10.5194/amt-10-59-2017, 2017.|
|15||Liu, J., et al., (2017), Contrasting carbon cycle responses of the tropical continents to the 2015-2016 El Nino, Science, 358(6360), eaam5690, doi: 10.1126/science.aam5690.|
|16||Washenfelder, R. A., Toon, G. C., Blavier, J. F., Yang, Z., Allen, N. T., Wennberg, P. O., Vay, S. A., Matross, D. M. & Daube, B. C., (2006), Carbon dioxide column abundances at the Wisconsin Tall Tower site. J. Geophys. Res. 111, D22305. doi:10.1029/2006JD007154.|
|17||Frankenberg, C., O’Dell, C., Guanter, L., and McDuffie, J., (2012), Remote sensing of near-infrared chlorophyll fluorescence from space in scattering atmospheres: implications for its retrieval and interferences with atmospheric CO2 retrievals, Atmospheric Measurement Techniques, 5(8): 2081–2094.|
|18||Frankenberg, C., Butz, A., and Toon, G. C., (2011a), Disentangling chlorophyll fluorescence from atmospheric scattering effects in O2 A‐band spectra of reflected sun‐light, Geophysical Research Letters, 38(3).|
|19||Joiner, J., et al., (2013), Global monitoring of terrestrial chlorophyll fluorescence from moderate-spectral-resolution near-infrared satellite measurements: Methodology, simulations, and application to GOME-2, Atmos. Meas. Tech., 6, 2803–2823, www.atmos-meas-tech.net/6/2803/2013/doi:10.5194/amt-6-2803-201.|
|20||Karion, A., Sweeney, C., Tans, P. P., and Newberger, T., (2010), AirCore: An Innovative Atmospheric Sampling System, Journal of Atmospheric and Oceanic Technology, 27, 1839–1853, doi:10.1175/2010JTECHA1448.1.|
|21||Köhler, P., et al., (2015), Simplified physically based retrieval of sun-induced chlorophyll fluorescence from GOSAT data, IEEE, 12(7).|
|22||Magney, T. S., Bowling, D. R., Logand, B. A., Grossmann, K., Stutz, J., Blanken, P. D., Burns, S. P., Cheng, R., Garcia, M. A., Köhler, P., Lopez, S., Parazoo, N. C., Raczka, B., Schimel, D., and Frankenberg, C., (2019), Mechanistic evidence for tracking the seasonality of photosynthesis with solar-induced fluorescence, Proc. Natl. Acad. Sci. USA, 11640–11645, doi:10.1073/pnas.1900278116.|
|23||O’Dell, C. W., Eldering, A., Wennberg, P. O., et al., (2018), Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 ACOS algorithm, Atmospheric Measurement Techniques, 11(12): 6539–6576.|