Summary

Description

Normalized Difference Vegetation Index (NDVI) Composites are produced from multiple Advanced Very High Resolution Radiometer (AVHRR) daily observations that have been composited together to create a nearly cloud-free image showing maximum greenness. An NDVI ratio is produced from bands one and two of the AVHRR composite to produce a derived NDVI band composite. The following NDVI products are available: Conterminous U.S. and Alaska Weekly and biweekly NDVI composites date from January 1989 to present. U.S. composites are cast to the Lambert Azimuthal Equal-Area projection. Alaska composites are cast to the Albers Equal-Area Conic projection. Distribution of the NDVI composites depends on the age of the image: 7- and 14-day (current) NDVI composites are weekly and biweekly updates produced within the last four weeks. The data includes a composite for each of the acquired AVHRR bands, as well as a derived NDVI band. 7- and 14-day (recent) NDVI composites are weekly and biweekly updates produced from the end of the previous year until four weeks prior to present. The data includes a composite for each of the acquired AVHRR bands, as well as a derived NDVI band. 14-day (historical) NDVI composites consist of biweekly composites produced from January 1989 to the end of the previous year. The data includes a composite for each of the acquired AVHRR bands, as well as a derived NDVI band. Satellite zenith, solar zenith, relative azimuth, and acquisition dates are also provided.