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Full catalog/MERGED_S3_OLCI_L3m_ILW
MERGED_S3_OLCI_L3m_ILW·v5.0·dataset

Color and health of lakes and rivers (Sentinel-3A+3B)

Merged Sentinel-3A and Sentinel-3B OLCI Regional Mapped Inland Waters (ILW) Data, version 5.0
biosphere NASA OB_CLOUD Level 3 active netCDF-4
In plain English

What it measures. Maps of the color and clarity of U.S. and Alaskan lakes and reservoirs, including surface reflectance and a Cyanobacteria Index that flags likely blue-green algae, plus harmful-algal-bloom flags.

How it's made. Produced by merging ocean-color observations from the OLCI instruments on the twin Sentinel-3A and Sentinel-3B satellites, corrected for atmospheric scattering and mapped over thousands of inland waterbodies.

How & where you'd use it. Helps monitor inland water quality and harmful algal blooms across thousands of lakes, and provides a standardized resource for developing and validating water-quality methods.

What's measured

Biological Classification › Bacteria/Archaea › Cyanobacteria (Blue-Green Algae)OCEANS › WATER QUALITY › ALGAL BLOOMS › HARMFUL ALGAL BLOOM (HABs)TERRESTRIAL HYDROSPHERE › WATER QUALITY/WATER CHEMISTRY › WATER CHARACTERISTICS › WATER COLOREARTH SCIENCE SERVICES › ENVIRONMENTAL ADVISORIES › HYDROLOGICAL ADVISORIES › WATER QUALITYTERRESTRIAL HYDROSPHERE › SURFACE WATER › SURFACE WATER FEATURES › LAKES/RESERVOIRSTERRESTRIAL HYDROSPHERE › SURFACE WATER › SURFACE WATER FEATURES › WETLANDSTERRESTRIAL HYDROSPHERE › GROUND WATERTERRESTRIAL HYDROSPHERE › SURFACE WATER › SURFACE WATER FEATURES › RIVERS/STREAMS

Coverage & cadence

  • Time span2016-04-25 → ongoing
  • Measured bySentinel-3A (OLCI) · Sentinel-3B
  • Processing levelLevel 3
  • Spatial extent-180, -90, 180, 90
  • FormatsnetCDF-4
  • StatusACTIVE

What you can do with it

  • Map vegetation, forests and biomass
  • Monitor ecosystem productivity and carbon
  • Support habitat and biodiversity studies
Official description

The ILW suite provides inland-water extractions for lakes and reservoirs across the contiguous U.S. (CONUS) and Alaska. ILW delivers Rayleigh-corrected surface reflectance (ρs, unitless) and the Cyanobacteria Index (CI_cyano, unitless). The data target for MERIS and OLCI are 15,450 CONUS waterbodies (≥1 full-resolution 300 m OLCI pixel), >2,300 larger resolvable lakes (≥3 pixels), and 5,874 resolvable lakes in Alaska—created in collaboration with the CyAN program to reduce user processing and provide a standardized resource for inland-water algorithm development, validation, and trend analysis. PACE OCI ILW targets 117 CONUS lakes (≥3 pixels) and lakes across Alaska. Geophysical variables in this suite include: - CI_cyano – Cyanobacteria Index, cyanobacteria only (Wynne & Stumpf algorithm, 2013) (sr⁻¹) - flags_habs – Harmful Algal Bloom flags (unitless / bitmask) - rhos_λ – Surface reflectance at wavelength λ (dimensionless)

Get the data

merged_s3_olci_l3m_ilw_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="MERGED_S3_OLCI_L3m_ILW",
    version="5.0",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from OB_CLOUD
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.