Level-0 - Reconstructed, unprocessed instrument data at full resolution
Level-1A - Level-0 data with ancillary information including time, geo-location, and calibration coefficients.
Level-1B - Level-1A data processed to sensor units (if applicable)
Level-2 - Derived geophysical variables at the same resolution and location as Level-1 source data
Level-3 - Variables mapped on uniform space-time grids, usually with some completeness and consistency
Level-4 - Model output or results from analyses of lower level data, including variables derived from two or more measurement