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Full catalog/MODIST_L4m_AVW
MODIST_L4m_AVW·v2022.0·dataset

Average color of the ocean's surface water (Terra)

Terra MODIS Level-4 Global Mapped Apparent Visible Wavelength (AVW) Data, version 2022.0
land NASA OB_CLOUD Level 4 active netCDF-4
In plain English

What it measures. A single number, in nanometers, that captures the overall color tone of surface ocean water. Lower values mean bluer, clearer water; higher values mean greener or browner, more productive or murkier water.

How it's made. Derived from ocean-color measurements by the MODIS sensor on NASA's Terra satellite and mapped onto a global grid.

How & where you'd use it. Used to classify water types, help pick the right algorithms for other ocean measurements, and detect regional changes. Interpretation is trickier in complex coastal waters.

What's measured

SPECTRAL/ENGINEERING › VISIBLE WAVELENGTHSOCEANS › OCEAN OPTICS › OCEAN COLORTERRESTRIAL HYDROSPHERE › WATER QUALITY/WATER CHEMISTRY › WATER CHARACTERISTICS › WATER COLORTERRESTRIAL HYDROSPHERE › WATER QUALITY/WATER CHEMISTRY › WATER CHARACTERISTICS › LIGHT TRANSMISSIONEARTH SCIENCE SERVICES › ENVIRONMENTAL ADVISORIES › HYDROLOGICAL ADVISORIES › WATER QUALITYTERRESTRIAL HYDROSPHERE › SURFACE WATER

Coverage & cadence

  • Time span2000-02-24 → ongoing
  • Measured byTerra (MODIS)
  • Processing levelLevel 4
  • Spatial extent-180, -90, 180, 90
  • FormatsnetCDF-4
  • StatusACTIVE

What you can do with it

  • Track deforestation, fire scars and land-cover change
  • Monitor crop and vegetation health (NDVI/EVI)
  • Map how built-up vs. green an area is over time
Official description

AVW (Apparent Visible Wavelength) quantifies the spectral “center” of ocean color by summarizing the shape of the water‐leaving reflectance spectrum (Rrs) across the visible range. Reported in nanometers (nm), AVW is lower for bluer, clearer (oligotrophic) waters and higher for greener/browner, more optically complex or productive waters influenced by phytoplankton, colored dissolved organic matter (CDOM), or suspended sediments. Users apply AVW for water-type classification, algorithm selection/blending (e.g., guiding chlorophyll retrievals), regional change detection, and as context alongside chlor_a, Kd_490, IOPs, and PAR. As with all ocean-color products, review quality flags (cloud/glint/aerosol) and note that interpretations can vary in optically complex coastal/inland waters. Geophysical variables in this suite include: - avw — Apparent Visible Wavelength (nm)

Get the data

modist_l4m_avw_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="MODIST_L4m_AVW",
    version="2022.0",
    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.