OCO-2¶

Orbiting Carbon Observatory-2 (OCO-2) Level 2 XCO2 (Lite FP, Standard) and Solar-Induced Fluorescence (Lite SIF), Build 11

Available

At a glance¶

Note on period: OCO-2 launched on 2014-07-02 and joined the A-Train on 2014-08-03. Lite XCO2 V11.2r files begin on 2014-09-06 and Lite SIF V11.2r on 2014-09-01. As checked on 2026-10-13, retrospective Lite XCO2 V11.3r runs through 2026-07-28, Lite SIF through 2026-07-27 and L2 Standard V11.2r through 2026-07-28, while the forward-stream XCO2 (OCO2_L2_Fwd_FP V11.3, from 2025-02-02) runs through 2026-10-10. Decontamination and manoeuvre periods leave gaps.

Overview¶

OCO-2 is NASA's carbon observatory. It measures reflected sunlight at high spectral resolution in the CO2 bands near 1.61 and 2.06 µm and the O2 A-band (0.76 µm), retrieving the column-averaged dry-air mole fraction of CO2 (XCO2) in soundings no larger than about 1.3 km × 2.25 km at nadir, almost a million per day. The same O2 A-band also yields solar-induced chlorophyll fluorescence (SIF), a proxy for photosynthetic activity. The project recommends the filtered, bias-corrected daily Lite files (XCO2: OCO2_L2_Lite_FP; SIF: OCO2_L2_Lite_SIF) for science, which are widely used for carbon-sink, urban and power-plant emission, and drought-impact studies.

What changes with the successor¶

OCO-2 Lite XCO2 V11.2r → OCO-2 Lite XCO2 V11.3r¶

Transition: 2026-06

V11.3r adds a bias-correction term for the negative XCO2 bias caused by ice building up on the focal plane arrays after 2024. The 2014–2023 record was not reprocessed, so a full-record analysis uses V11.2r through 2023 and V11.3r from 2024.

Sources: OCO-2 Level 2 Data Release Statement v11.3 (Rev A, 2026-06) · OCO-2 V11.2 / OCO-3 V11 L2 Data User's Guide (v04 Rev B, 2026-06-10)

Available variables¶

XCO2 Lite variables follow the OCO-2 L2 Data User's Guide (V11.2/V11.3) and the Lite file product description (V8r, 2017); SIF Lite variables follow Table 4-1 of the SIF V11.2 User's Guide. Sounding/, Retrieval/, Science/ and Metadata/ are netCDF4 groups. Some readers do not show groups; use an HDF5 tool or xarray's group argument.

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

XCO2 Lite (OCO2_L2_Lite_FP, daily netCDF4)¶

SIF Lite (OCO2_L2_Lite_SIF, daily netCDF4)¶

The full variable list is in the official documentation.

How to get the data¶

• NASA GES DISC — OCO2_L2_Lite_FP V11.3r (2024 onward) — HTTPS / earthaccess / Earthdata Search / OPeNDAP (Earthdata Cloud)
  • For 2014–2023 use OCO2_L2_Lite_FP V11.2r (https://disc.gsfc.nasa.gov/datasets/OCO2_L2_Lite_FP_11.2r/summary). Files are named oco2_LtCO2_YYMMDD_B11300Ar_.nc4 (B112xxAr for V11.2r). A free Earthdata Login is required.
• NASA GES DISC — OCO2_L2_Lite_SIF V11.2r — HTTPS / earthaccess / Earthdata Search
  • Files are named oco2_LtSIF_YYMMDD_B112xxAr_.nc4.
• NASA GES DISC — OCO2_L2_Standard V11.2r — HTTPS / earthaccess (HDF5, one file per orbit and mode segment)
  • Expert files with all retrieval diagnostics. Values are not bias-corrected, so the project recommends the Lite files for general use. V11.2r starts on 2019-11-30; V11r (2014-09 to 2024-04-01), which covers earlier years, is still in CMR.
• NASA GES DISC — forward stream OCO2_L2_Fwd_FP V11.3 — HTTPS / earthaccess
  • Since June 2025, bias-corrected daily forward files appear within a week of observation. Replace them with retrospective files when available. No DOI.
• NASA Earthdata Search — Web search, spatial/temporal subsetting, bulk download
• OCO-2 project site (NASA JPL) — Mission news, documents and science highlights
  • Since August 2026, operations news also appears on the Caltech OCO site (https://oco.caltech.edu/).

Example code¶

Downloads Lite XCO2 (V11.3r) around Korea for July 2024 with earthaccess and keeps only soundings with quality flag 0. The first run asks for your Earthdata credentials. For years up to 2023, use version="11.2r".

import earthaccess
import xarray as xr
import numpy as np

earthaccess.login()  # free NASA Earthdata account
results = earthaccess.search_data(
    short_name="OCO2_L2_Lite_FP", version="11.3r",
    temporal=("2024-07-01", "2024-07-31"),
    bounding_box=(120, 30, 135, 45),   # (west, south, east, north)
)
files = earthaccess.download(results, "oco2_lite")

out = []
for f in files:
    ds = xr.open_dataset(f)                         # root-level variables (xco2, latitude, ...)
    good = (ds["xco2_quality_flag"] == 0) \
        & ds["latitude"].between(30, 45) & ds["longitude"].between(120, 135)
    out.append(ds[["xco2", "xco2_uncertainty", "latitude", "longitude", "time"]].where(good, drop=True))
    # Mode and land fraction live in a group:
    # snd = xr.open_dataset(f, group="Sounding"); snd["operation_mode"]

sel = xr.concat(out, dim=out[0]["xco2"].dims[0])   # concatenate along the sounding dimension
print(sel.sizes, float(sel["xco2"].mean()))

Practical tips¶

• Use xco2 from the Lite files (bias-corrected and filtered). Retrieval/xco2_raw and the XCO2 in L2 Standard are pre-correction values and should not be used as is.
• Start with xco2_quality_flag = 0. Land and ocean-glint soundings have different bias behaviour, so compare them by mode (Sounding/operation_mode) before averaging them together.
• Use V11.3r from 2024 onward. With no decontamination between February 2023 and February 2025, detector icing biased V11.2 XCO2 low by up to about 0.5 ppm. Decontaminations are now planned yearly.
• According to the User's Guide, the Lite files include an XCO2 converted to the WMO X2019 CO2 scale (about 0.08 ppm higher than X2007). The scale of xco2 is given in its comment attribute; match scales when comparing with NOAA or TCCON data.
• xco2_uncertainty is the retrieval's posterior error, which the product description says is generally 30–50% smaller than the true uncertainty. Do not use it unadjusted for error propagation or inversion weights.
• Cloudy and aerosol-laden regions (the East Asian summer monsoon, the tropics) yield far fewer valid soundings. Report sample counts with any regional mean.
• OCO-3 (on the International Space Station's JEM-EF since 2019) is OCO-2's sister instrument. It samples latitudes below about 52° at varying times of day and has a snapshot area map (SAM) mode for cities. There are no data during its storage period from November 2023 to July 2024 (science resumed 16 July 2024). Its data are separate OCO-3 collections at GES DISC.
• SIF_740nm is the easiest SIF quantity to compare with other sensors such as TROPOMI. For comparisons with GPP, use Daily_SIF_* rather than instantaneous values and state the clear-sky assumption.

Notices and change history¶

References for your paper¶

Dataset citation¶

OCO-2 Lite XCO2 V11.3r (2024 onward) — DOI 10.5067/C4OENLFCYVSA

@misc{oco2_lite_fp_v113r,
  author    = {{OCO-2/OCO-3 Science Team} and Payne, Vivienne and Chatterjee, Abhishek},
  title     = {{OCO-2} Level 2 bias-corrected {XCO2} and other select fields from the full-physics retrieval aggregated as daily files, Retrospective processing {V11.3r}},
  year      = {2026},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/C4OENLFCYVSA}
}

OCO-2 Lite XCO2 V11.2r (2014–2023) — DOI 10.5067/70K2B2W8MNGY

@misc{oco2_lite_fp_v112r,
  author    = {{OCO-2/OCO-3 Science Team} and Payne, Vivienne and Chatterjee, Abhishek},
  title     = {{OCO-2} Level 2 bias-corrected {XCO2} and other select fields from the full-physics retrieval aggregated as daily files, Retrospective processing {V11.2r}},
  year      = {2024},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/70K2B2W8MNGY}
}

OCO-2 Lite SIF V11.2r — DOI 10.5067/8XXUQU7HBGBL

@misc{oco2_lite_sif_v112r,
  author    = {{OCO-2/OCO-3 Science Team} and Payne, Vivienne and Chatterjee, Abhishek},
  title     = {{OCO-2} Level 2 bias-corrected solar-induced fluorescence and other select fields from the {IMAP-DOAS} algorithm aggregated as daily files, Retrospective processing {V11.2r}},
  year      = {2024},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/8XXUQU7HBGBL}
}

OCO-2 L2 Standard V11.2r — DOI 10.5067/WVNRFIYMRJE1

@misc{oco2_l2std_v112r,
  author    = {{OCO-2/OCO-3 Science Team} and Payne, Vivienne and Chatterjee, Abhishek},
  title     = {{OCO-2} Level 2 geolocated {XCO2} retrievals results, physical model Retrospective Processing {V11.2r}},
  year      = {2024},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/WVNRFIYMRJE1}
}

Reference papers¶

ACOS retrieval algorithm (V8, AMT) — DOI 10.5194/amt-11-6539-2018

@article{odell2018acos,
  author  = {O'Dell, Christopher W. and Eldering, Annmarie and Wennberg, Paul O. and Crisp, David and Gunson, Michael R. and Fisher, Brendan and others},
  title   = {Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 {ACOS} algorithm},
  journal = {Atmospheric Measurement Techniques},
  volume  = {11},
  number  = {12},
  pages   = {6539--6576},
  year    = {2018},
  doi     = {10.5194/amt-11-6539-2018}
}

OCO-2 on-orbit instrument performance (AMT) — DOI 10.5194/amt-10-59-2017

@article{crisp2017oco2,
  author  = {Crisp, David and Pollock, Harold R. and Rosenberg, Robert and Chapsky, Lars and Lee, Richard A. M. and Oyafuso, Fabiano A. and others},
  title   = {The on-orbit performance of the Orbiting Carbon Observatory-2 ({OCO-2}) instrument and its radiometrically calibrated products},
  journal = {Atmospheric Measurement Techniques},
  volume  = {10},
  number  = {1},
  pages   = {59--81},
  year    = {2017},
  doi     = {10.5194/amt-10-59-2017}
}

Acknowledgements¶

Cite the GES DISC dataset DOI for each product and version used (both DOIs if you combine V11.2r for 2014–2023 with V11.3r from 2024). It is customary to cite O'Dell et al. (2018) and the GES DISC ATBD for the retrieval, and Crisp et al. (2017) for the instrument and calibration.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• OCO-2 project site (JPL)
• Caltech OCO site
• NASA Science — OCO-2 mission page
• OCO-2 V11.2 / OCO-3 V11 L2 Data User's Guide (2026-06-10)
• OCO-2 L2 Data Release Statement v11.3
• OCO-2 SIF v11.2 / OCO-3 v11 User's Guide
• OCO L2 ATBD
• OCO Known Data Issues
• OCO-3 (NASA Science mission page)
• OCO-3 project site (JPL)