PACE OCI Ocean Color¶

PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) Ocean Color Instrument (OCI) Level-2 and Level-3 ocean products (AOP, IOP, BGC, KD, PAR) and Level-4 MOANA and NPP_CAFE, version 3.2 (NASA hyperspectral ocean color)

Available

At a glance¶

Note on period: PACE launched on 2024-02-08 and its data were first released on 2024-04-11 (V1). When checked on 2026-10-13, every V3.2 Level-2, Level-3 and Level-4 collection begins on 2024-03-05. A spacecraft safe hold stopped science collection from 22:40 UTC on 2024-05-24 (instrument recovery began on 28 May), and a safe hold on 2026-02-09 left a data gap on 2026-02-10.

Overview¶

PACE is a NASA ocean and atmosphere satellite launched in February 2024. Its main sensor, OCI, is a hyperspectral spectrometer that measures continuously from the ultraviolet to the near infrared (340–895 nm) in 2.5 nm steps with 5 nm bandwidth, plus seven shortwave infrared bands (940–2260 nm). This page covers the OCI ocean products made by OBPG: hyperspectral remote sensing reflectance (Rrs) with fluorescence line height and apparent visible wavelength (AOP), inherent optical properties such as absorption and backscattering (IOP), diffuse attenuation (Kd), chlorophyll a, phytoplankton carbon and particulate organic and inorganic carbon (BGC), photosynthetically available radiation (PAR), picophytoplankton community composition (MOANA) and net primary production (NPP_CAFE). They carry the NASA ocean color record from SeaWiFS, MODIS and VIIRS into the hyperspectral era. The OCI aerosol (UAA), cloud, trace gas (NO2, O3) and land products, and the aerosol and cloud products from the HARP2 and SPEXone polarimeters, are separate collections and are not covered here.

What changes with the successor¶

PACE OCI V2 → PACE OCI V3.0¶

Transition: 2025-02

A full-mission reprocessing that recalibrated OCI using only on-orbit solar diffuser data and applied system vicarious calibration (SVC) gains for the first time. Rrs atmospheric correction changed in several ways, some wavelengths were removed, and several products were raised to Provisional.

Sources: OBPG — PACE Science Data Reprocessing Version 3 · PACE — OCI Version 3 (V3) Reprocessing announcement · PACE Science Data V2 Release Notes

PACE OCI V3.0 → PACE OCI V3.1¶

Transition: 2025-08

Level-2 and Level-3 remade after adding a 650–900 nm ghosting correction to Level-1B (V3.0.1) and fixing the vicarious gains (red over-calibration). NRT switched to V3.1 from 2025-07-02 data and the full mission was reprocessed.

Sources: PACE — OCI V3.1 Reprocessing and New Product Release (2025-08-26) · PACE OCI V3 Release Notes

PACE OCI V3.1 → PACE OCI V3.2¶

Transition: 2026-04

An ocean-product reprocessing that fixed a BRDF implementation error in spectral Rrs. Cross-scan artifacts dropped, the Level-3 AOP, IOP and BGC suites each became one file, and pic was added.

Sources: Earthdata — PACE ocean color products have been reprocessed (V3.2) · PACE OCI V3 Release Notes (V3.2 changes)

Available variables¶

Variable names and units come from the V3.2 L3m and L4m files (OB.DAAC OPeNDAP attributes) and the PACE OCI V3 release notes, which rate most ocean products as Provisional (reviewed but not yet validated). Level-2 files hold the same variables in the geophysical_data group, with latitude and longitude in the navigation_data group.

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

L3m apparent optical properties (AOP file, PACE_OCI_L3M_AOP)¶

L3m inherent optical properties (IOP file, PACE_OCI_L3M_IOP)¶

L3m diffuse attenuation (KD file, PACE_OCI_L3M_KD)¶

L3m biogeochemical properties (BGC file, PACE_OCI_L3M_BGC)¶

L3m photosynthetically available radiation (PAR file, PACE_OCI_L3M_PAR)¶

L4m phytoplankton community and net primary production (PACE_OCI_L4M_MOANA, NPP_CAFE)¶

L2 swath (OC_AOP, OC_IOP, OC_BGC and PAR 5-minute granules)¶

The full variable list is in the official documentation.

How to get the data¶

• NASA Earthdata Search (OB.DAAC portal) — Web search and download, earthaccess (Python; short names such as PACE_OCI_L3M_BGC or PACE_OCI_L2_AOP), Harmony subsetting (Level-2)
  • Collections are PACE_OCI_L2_{AOP,IOP,BGC,PAR}, PACE_OCI_L3M_{AOP,IOP,KD,BGC,PAR} and PACE_OCI_L4M_{MOANA,NPP_CAFE}, each with an _NRT counterpart. According to the Help Hub FAQ, Harmony does not yet support spatial subsetting of Level-3 mapped data. A free NASA Earthdata Login is required.
• OB.DAAC Direct Data Access (Level-3 Mapped / PACE-OCI) — HTTPS directories by year and day, e.g. PACE_OCI.20260801_20260831.L3m.MO.BGC.V3_2.0p1deg.nc
  • The Level-2 and Level-4 Mapped folders follow the same layout. Downloads require an Earthdata Login.
• OB.DAAC File Search — File lists by name pattern, date range and region (for wget or curl)
• OB.DAAC OPeNDAP (L3 SMI and L4 SMI) — OPeNDAP (year/MMDD folders, e.g. L3SMI/2026/0801/)
  • Level-4 files are under /opendap/PACE_OCI/L4SMI/.
• OB.DAAC Level 3 & 4 Browser — Web map previews and file selection (choose Provisional under Product Status)

Example code¶

Downloads a V3.2 L3m monthly BGC file (0.1°) with earthaccess and looks at chlorophyll around the Korean Peninsula. Run earthaccess.login() once with your NASA Earthdata account. Latitude in L3m files runs from north to south, so slice it as slice(north, south).

# pip install earthaccess xarray netCDF4
import earthaccess
import xarray as xr

earthaccess.login()
results = earthaccess.search_data(
    short_name="PACE_OCI_L3M_BGC",           # Rrs is in PACE_OCI_L3M_AOP
    temporal=("2025-05-01", "2025-05-31"),
    granule_name="*.MO.BGC.V3_2.0p1deg.nc",   # daily: *.DAY.*, 8-day: *.8D.*, 4km: *.4km.nc
)
paths = earthaccess.download(results, local_path="pace")

ds = xr.open_dataset(paths[0])
chl = ds["chlor_a"].sel(lat=slice(40, 30), lon=slice(120, 132))   # around Korea
print(float(chl.median()), int(chl.count()))

# For an AOP file: ds["Rrs"].sel(wavelength=443, method="nearest")

Practical tips¶

• Do not mix versions. V3.2 fixed a BRDF correction that ignored changes in relative azimuth across the scan, which substantially changed Rrs accuracy and cross-track stability. Files downloaded before V3.2 are best replaced (check for V3_2 in the file name).
• Rrs below 400 nm is not validated and may carry significant biases. Rrs at 590–610 nm has been removed since V3 because of the discontinuity between the blue and red focal planes.
• Red-wavelength Rrs may keep residual water vapour and oxygen absorption artifacts, and nflh is affected by scan-edge reflectance errors and the 680 nm O2 b-band (known issues in the V3.2 alert).
• Elevated red reflectance near the scan edges at high view zenith angles is flagged in Level-2 and masked in Level-3 above 60°. Check the flags if you work with Level-2 directly.
• The CMR description warns that BGC retrievals carry higher uncertainty in coastal and inland waters and under heavy aerosol or glint. Be especially careful with chlorophyll in the turbid coastal Yellow Sea and East China Sea and during spring dust events, and check the quality flags.
• V3.2 added a coccolithophore flag to Level-2. BGC values there may be biased, and the coccolithophore mask is not applied to Level-3 AOP.
• MOANA (picophytoplankton community) covers only the Atlantic (70°S–70°N, 85°W–25°E), so it has no values around Korea.
• chlor_a uses the same OBPG standard algorithm family as MODIS and VIIRS ocean color (CI at low concentrations, OCx band ratio at higher), which eases comparison, but sensors, calibration and versions differ. Check the differences over an overlap period before joining records.
• From V3.2 each Level-3 AOP, IOP and BGC file holds all variables of its suite. Rrs in a 4km AOP file is a 4320×8640×172 array, so use the 0p1deg files for broad-scale patterns.
• Safe holds left gaps from 22:40 UTC on 2024-05-24 to at least 28 May and on 2026-02-10. Check how many cells are empty in daily and 8-day composites for those periods.

Notices and change history¶

References for your paper¶

Dataset citation¶

PACE OCI L3m Ocean Biogeochemical Properties V3.2 — DOI 10.5067/PACE/OCI/L3M/OC_BGC/3.2

@misc{obpg2026paceocil3mbgc,
  author    = {{NASA Ocean Biology Processing Group}},
  title     = {{PACE} {OCI} Level-3 Global Mapped Ocean Biogeochemical Properties Data, version 3.2},
  year      = {2026},
  publisher = {NASA Ocean Biology Distributed Active Archive Center},
  version   = {3.2},
  doi       = {10.5067/PACE/OCI/L3M/OC_BGC/3.2}
}

PACE OCI L3m Apparent Optical Properties (Rrs) V3.2 — DOI 10.5067/PACE/OCI/L3M/OC_AOP/3.2

@misc{obpg2026paceocil3maop,
  author    = {{NASA Ocean Biology Processing Group}},
  title     = {{PACE} {OCI} Level-3 Global Mapped Apparent Optical Properties Data, version 3.2},
  year      = {2026},
  publisher = {NASA Ocean Biology Distributed Active Archive Center},
  version   = {3.2},
  doi       = {10.5067/PACE/OCI/L3M/OC_AOP/3.2}
}

PACE OCI L2 Apparent Optical Properties V3.2 — DOI 10.5067/PACE/OCI/L2/OC_AOP/3.2

@misc{obpg2026paceocil2aop,
  author    = {{NASA Ocean Biology Processing Group}},
  title     = {{PACE} {OCI} Level-2 Regional Apparent Optical Properties Data, version 3.2},
  year      = {2026},
  publisher = {NASA Ocean Biology Distributed Active Archive Center},
  version   = {3.2},
  doi       = {10.5067/PACE/OCI/L2/OC_AOP/3.2}
}

Reference papers¶

PACE mission overview — DOI 10.1175/BAMS-D-18-0056.1

@article{werdell2019pace,
  author  = {Werdell, P. Jeremy and Behrenfeld, Michael J. and Bontempi, Paula S. and Boss, Emmanuel and Cairns, Brian and Davis, Gary T. and Franz, Bryan A. and Gliese, Ulrik B. and Gorman, Eric T. and Hasekamp, Otto and Knobelspiesse, Kirk D. and Mannino, Antonio and Martins, J. Vanderlei and McClain, Charles R. and Meister, Gerhard and Remer, Lorraine A.},
  title   = {The Plankton, Aerosol, Cloud, Ocean Ecosystem Mission: Status, Science, Advances},
  journal = {Bulletin of the American Meteorological Society},
  volume  = {100},
  number  = {9},
  pages   = {1775--1794},
  year    = {2019},
  doi     = {10.1175/BAMS-D-18-0056.1}
}

Chlorophyll CI algorithm (low-concentration chlor_a) — DOI 10.1029/2011JC007395

@article{hu2012ci,
  author  = {Hu, Chuanmin and Lee, Zhongping and Franz, Bryan},
  title   = {Chlorophyll a algorithms for oligotrophic oceans: A novel approach based on three-band reflectance difference},
  journal = {Journal of Geophysical Research: Oceans},
  volume  = {117},
  number  = {C1},
  year    = {2012},
  doi     = {10.1029/2011JC007395}
}

Acknowledgements¶

OBPG asks that datasets be cited as author (NASA Ocean Biology Processing Group), release date, dataset title, publisher (NASA OB.DAAC), DOI and date accessed, and that published work include a general acknowledgement of OBPG/OB.DAAC for data before the reference list (no fixed wording is given).

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¶

• PACE — Access PACE Data and release notes
• PACE — Data products overview (DOIs by suite)
• OBPG — PACE Version 3 reprocessing
• PACE OCI V3 Release Notes (PDF)
• Oceandata Help Hub (PACE notebooks and FAQ)
• About the OCI instrument
• OBPG chlorophyll a ATBD
• This site — MODIS ocean color (earlier multispectral record)
• This site — VIIRS ocean color (current multispectral record)