The Level-3 MODIS Atmosphere Eight-Day Global Product contains nearly 1000 statistical datasets (SDS's) that are derived from the Level-3 MODIS Atmosphere Daily Global Product. There are two MODIS Eight Day Global data product files: MOD08_E3, containing data collected from the Terra platform; and MYD08_E3, containing data collected from the Aqua platform.

Statistics are sorted into 1x1 degree cells on an equal-angle grid that spans an 8-day interval and then summarized over the globe. It should be noted that the eight-day interval start date is reset to January 1^st at the beginning of every new year.

Computed Statistics 

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

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)