The Level-3 MODIS Atmosphere Daily Global Product contains roughly 600 statistical datasets that are derived from approximately 80 scientific parameters from four Level-2 MODIS Atmosphere Products: Aerosol, Water Vapor, Cloud, and Atmosphere Profile. There are two MODIS Daily Global data product files: MOD08_D3, containing data collected from the Terra platform; and MYD08_D3, containing data collected from the Aqua platform.
A range of statistical summaries are computed, depending on the parameter being considered. Statistics for a given measurement might include:
- Simple (mean, minimum, maximum, standard deviation) statistics
- Parameters of normal and log-normal distributions
- Fraction of pixels that satisfy some condition (e.g. cloudy, clear)
- Histograms of the quantity within each grid box
- Histograms of the confidence placed in each measurement
- Histograms and/or regressions derived from comparing one science parameter to another, statistics may be computed for a subset that satisfies some condition
Statistics are sorted into 1 by 1 degree cells on an equal-angle grid that spans a 24-hour (0000 to 2400 Greenwich Mean Time) interval and then summarized over the globe. It should be noted that browse images (see links at left) are available in both the native equal-angle (lat-lon) grid as well as an equal-area (hammer-aitoff) grid.
Data Documentation (Primer on Computation)
Users working with Level-3 (L3) Daily, Eight-day, or Monthly Global Gridded MODIS data (at 1 degree resolution) are advised to become familiar with the Level-3 Algorithm Theoretical Basis Document. This document details characteristics, properties, and content of Level-3 data. Also included in this document are user caveats and frequently asked questions. The L3 ATBD is linked on the above 'QA Plan & ATBDs' page, as well as individual 'Theoretical Basis' pages in the L3 product sections. The link for the 'Theoretical Basis' page in the L3 Monthly product section is provided below. It should be noted that there is only one L3 ATBD for all L3 products (Daily, Eight-day, & Monthly).
L3 ATBD (L3 primer)