MOD13 Vegetation Indices (MODIS NDVI/EVI)

MOD13 is the MODIS Vegetation Indices product suite distributed by NASA, providing 16-day composite NDVI and EVI layers at multiple spatial resolutions.^[1] The flagship products are MOD13Q1 (Terra) and MYD13Q1 (Aqua) at 250 m GSD.^[1][2] The full product family spans 500 m (MOD13A1/MYD13A1), 1000 m (MOD13A2/MYD13A2), and 0.05-degree Climate Modelling Grid variants (MOD13C1/MYD13C1/MOD13A3/MYD13A3/MOD13C2).^[3] Collection 6.1 (v061) is the current version and is the form available via NASA Earthdata and Google Earth Engine.^[4]

The archive extends from 2000 (Terra) and 2002 (Aqua) to present, providing one of the longest satellite-derived vegetation index records at consistent spatial resolution.^[3] Terra and Aqua VI values differ systematically due to equatorial crossing time differences and are not interchangeable without cross-calibration. Products are distributed in HDF-EOS2 format on the native MODIS Sinusoidal grid; users requiring standard geographic projections must reproject, though the CMG variants are provided in geographic coordinates directly.^[1]

Cloud persistence despite the 16-day compositing window can degrade product quality in the equatorial belt; pixel reliability flags (SummaryQA and DetailedQA layers) must be applied to exclude poor-quality retrievals.^[3] Snow commission affects EVI differently than NDVI; EVI values increase over snow-covered surfaces, which can inflate boreal and alpine winter composites. The 16-day cadence and 250 m resolution are suited to landscape-scale phenology and long-term trend analysis rather than near-real-time alert applications.