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Full catalog/CLDMSK_L2_VIIRS_NOAA20
CLDMSK_L2_VIIRS_NOAA20·v2·dataset

Which pixels are cloudy vs clear (VIIRS, NOAA-20)

VIIRS/NOAA20 Cloud Mask and Spectral Test Results 6-Min L2 Swath 750m V2
atmosphere NASA LAADS Level 2 active NetCDF-4
In plain English

What it measures. A pixel-by-pixel judgment of which parts of a scene are cloudy versus clear, at 750-meter detail (with a finer 375-meter daytime version), along with the spectral test results behind each call.

How it's made. Produced from VIIRS data on the NOAA-20 satellite using a cloud-detection algorithm built to work consistently across MODIS and VIIRS so records line up over time.

How & where you'd use it. A behind-the-scenes input that lets other products screen out clouds; most people benefit from it indirectly through cleaner land, ocean, and atmosphere data.

What's measured

ATMOSPHERE › CLOUDSATMOSPHERE › CLOUDS › CLOUD PROPERTIES › CLOUD FREQUENCYATMOSPHERE › CLOUDS › CLOUD PROPERTIES › CLOUD HEIGHTSPECTRAL/ENGINEERING › INFRARED WAVELENGTHS › INFRARED RADIANCESPECTRAL/ENGINEERING › INFRARED WAVELENGTHS › REFLECTED INFRAREDSPECTRAL/ENGINEERING › VISIBLE WAVELENGTHS › VISIBLE RADIANCE

Coverage & cadence

  • Time span2018-02-17 → ongoing
  • Measured byNOAA-20 (VIIRS)
  • Processing levelLevel 2
  • Spatial extent-180, -90, 180, 90
  • FormatsNetCDF-4
  • StatusACTIVE

What you can do with it

  • Map air pollutants — NO₂, aerosols, ozone
  • Track greenhouse gases and Earth's energy budget
  • Feed weather and air-quality analysis
Official description

The National Oceanic and Atmospheric Administration-20 (NOAA-20) Visible Infrared Imaging Radiometer Suite (VIIRS) NASA Level-2 (L2) Cloud Mask is one of four continuity products designed to sustain the long-term records of both Moderate Resolution Imaging Spectroradiometer (MODIS) and VIIRS heritages. CLDMSK_L2_VIIRS_NOAA20 is the shortname for the NOAA-20 VIIRS incarnation of the Cloud Mask continuity product that is derived from the MODIS-VIIRS cloud mask (MVCM) continuity algorithm, which itself is based on the MODIS (MOD35) algorithm. The MODIS (from Terra and Aqua missions) and VIIRS (from SNPP and Joint Polar Satellite System (JPSS) missions) data-derived cloud mask products use the MVCM algorithm. Implemented to consistently handle MODIS and VIIRS inputs, the NOAA-20 VIIRS v2.0 collection products use calibration-adjusted NASA VIIRS L1B as inputs. The nominal spatial resolution of the NOAA-20 VIIRS L2 Cloud mask is 750 meters at nadir. The v2.0 collection, which starts from February 17, 2018 (2018-048), also contains a high-resolution I-band (375 m) daytime cloud mask. The L2 netCDF product, acquired and processed every 6 minutes. Consult the [MODIS-VIIRS Cloud Mask Product User Guide](https://ladsweb.modaps.eosdis.nasa.gov/api/v2/content/archives/Document%20Archive/Science%20Data%20Product%20Documentation/MVCM_User_Guide_Oct_2020.pdf) for additional information regarding the transition from the MODIS-MOD35 to the MVCM algorithm, inputs to MVCM, output files, file naming conventions, quality flags, and validation. Users are also encouraged to consult the MOD35 Algorithm Theoretical Basis Document ([ATBD](https://modis-atmosphere.gsfc.nasa.gov/sites/default/files/ModAtmo/MOD35_ATBD_Collection6_0.pdf)) and the [MODIS Atmosphere QA Plan](https://modis-atmosphere.gsfc.nasa.gov/sites/default/files/ModAtmo/QA_Plan_C6_Master_2015_05_05_0.pdf) for relevant information that are applicable to the NOAA-20 VIIRS Cloud Mask product.

Get the data

cldmsk_l2_viirs_noaa20_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="CLDMSK_L2_VIIRS_NOAA20",
    version="2",
    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 LAADS
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.