[Source: NASA Atmospheric Science Data Center, http://eosweb.larc.nasa.gov/GUIDE/dataset_documents/cer_isccp-d2lik...
The Monthly Gridded Cloud Averages (ISCCP-D2like-day/nit), archival data product contains 3-hourly (GMT based) monthly and monthly 1° gridded regional mean cloud properties as a function of 18 cloud types, similar to the ISCCP D2 product, where the ... cloud properties are stratified by pressure, optical depth and phase. There is a dataset for Terra-MODIS and Aqua-MODIS as well as a day and nighttime dataset. The retrievals and therefore the quality are different for each dataset. For the MODIS based ISCCP D2-like products the cloud amounts for 42 cloud types, similar to the ISCCP D1 product, is also available. Input to the Subsystem is the Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) archival data product. Each ISCCP-D2like covers a single month, using the SSF based on the CERES instrument, which is in cross-track scan mode. The science data are Scientific Data Sets (SDSs) with multiple records. Each record contains spatially averaged data for an individual region. The following tables are helpful in recognizing the structure of the HDF output.