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Full catalog/VIIRSJ2_L3m_RRS_NRT
VIIRSJ2_L3m_RRS_NRT·v2025.0·dataset

Color of the ocean surface (NOAA-21, near-real-time)

NOAA-21 VIIRS Level-3 Global Mapped Remote-Sensing Reflectance (RRS) - Near Real-time (NRT) Data, version 2025.0
ocean NASA OB_CLOUD Level 3 active netCDF-4
In plain English

What it measures. The color of the ocean surface — how much light leaves the water at each wavelength relative to incoming sunlight. This is the basic raw signal underlying most ocean-color products.

How it's made. Measured by the VIIRS instrument on NOAA-21 and delivered as a fast, near-real-time global map, so the calibration is rougher than the final version.

How & where you'd use it. A foundational input that scientists convert into things like algae levels and water clarity; the near-real-time release is handy for timely monitoring, with care needed in murky coastal waters.

What's measured

Oceans › Ocean Optics › Reflectance

Coverage & cadence

  • Time span2022-11-10 → ongoing
  • Measured byNOAA-21 (VIIRS)
  • Processing levelLevel 3
  • Spatial extent-180, -90, 180, 90
  • FormatsnetCDF-4
  • StatusACTIVE

What you can do with it

  • Watch sea-surface temperature and marine heatwaves
  • Spot algal blooms and ocean-colour shifts
  • Support fisheries and coastal monitoring
Official description

The Ocean Biology DAAC produces near real-time (NRT) products using the best-available combination of ancillary data from meteorological and ozone data. As such, the inputs and the calibration used are less than optimal. Near real-time products provide a snapshot of the data during a short time period within a single orbit. The Remote Sensing Reflectance (RRS) suite provides the remote sensing reflectance at wavelength λ (nm)—the ratio of water-leaving radiance to downwelling irradiance just above the surface (units sr⁻¹). Variables are named by their band center (e.g., Rrs_412, Rrs_443). Rrs_λ is the foundational observable used to retrieve products such as chlor_a, Kd_490, IOPs, and to support algorithm development, validation, water-quality, and ecosystem applications. Users should review per-file quality flags (e.g., land, cloud, sun glint, high aerosol) and mission documentation—especially in optically complex coastal/inland waters. Geophysical variables in this suite include: - Rrs — Remote sensing reflectance (sr⁻¹)

Get the data

viirsj2_l3m_rrs_nrt_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="VIIRSJ2_L3m_RRS_NRT",
    version="2025.0",
    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.