The National Oceanic and Atmospheric Administration (NOAA) 20 Visible Infrared Imaging Radiometer Suite (VIIRS) NASA Level-3 (L3) monthly Cloud Properties is a continuity product designed to sustain the long-term records of both Moderate Resolution Imaging Spectroradiometer (MODIS) and VIIRS heritages. CLDPROP_M3_VIIRS_NOAA20 is the short name for the NOAA-20 VIIRS incarnation of the monthly-aggregated Level-3 (identified by M3) Cloud Properties continuity product. CLDPROP is used to represent Cloud Properties, which includes both Cloud-Optical Property (COP) and Cloud-Top Property parameters. This product ensures continuity of approach through a common algorithm that is applicable to both MODIS and VIIRS data by leveraging only those spectral channels that are common to both instruments.

The L3 monthly Cloud Properties product is derived by aggregating the NOAA-20/VIIRS D3 Cloud Properties product (CLDPROP_D3_VIIRS_NOAA20), which is a global gridded dataset that is produced daily. This monthly product contains 128 science data sets (SDS/parameters) that comprise 837 variables (statistics). The number of science parameters broadly breakdown thus:

• Cloud-Top Properties: 21
• Cloud-Optical Properties: 103
• Solar and Sensor Angles: 4

Each science parameter may include a combination of the following statistical variables:

• Mean, standard deviation, pixel count, sum, and sum squares
• Parameters of log-normal distributions
• Fraction of pixels that satisfy some condition (e.g., liquid water clouds, ice clouds, etc.)
• Histograms of the sampled Level-2 pixels within each grid-cell
• Joint histograms that are derived by comparing one science parameter to another; this may also involve computing statistics for a subset that satisfies some condition.

Consult the Level-3 Continuity Cloud Properties (CLDPROP_L3) Gridded Products User Guide for details regarding how the L3 monthly statistics are computed, and to learn more about the gridding and sampling protocols specific to this product besides a number of other topics relevant to the user community. Each calendar year includes 12 granules. The version 1.1 collection of this product starts from March 17, 2018 (Julian day 076).