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  Vegetation Condition from AVHRR NDVI Data


Vegetation Condition images for the United States based on NDVI (Normalized Difference Vegetation Index) are available for viewing at this site. The NDVI measures vegetation vigor caused by chlorophyll activity; this is sometimes called "greenness". These data have proven valuable to USDA policy officials in providing geographic location and monitoring information for vegetation condition in cropland and pasture regions throughout the growing season. The SAGA group, Agriculture Division of Statistics Canada, maintains a similar program for Canada called the Crop Condition Assessment Program. For a worldwide view, see Crop Explorer provided by the IPA division of USDA's Foreign Agricultural Service.

The Vegetation Condition data selectable below are updated weekly and arranged by two week composite periods covering the 1995 - 1999, 2001-2003, 2004-2009, 2010, and 2012 (as available) crop seasons. A water vapor correction was applied by USGS to data collected by NOAA-14 from the 1995 through the 1999 crop season. Data from subsequent satellites (NOAA-16, NOAA-17, NOAA-18) are not water vapor corrected. Ratio derived products of a specific period to a previous comparable date period are only created within images of the same satellite.

The NOAA-16 satellite collected images from the 2001 through 2003 seasons. NOAA-16 started malfunctioning in early 2004, when a scan motor problem caused a 'barcode' appearance. Images from the NOAA-17 satellite replaced NOAA-16 starting in 2004. The USGS released updated calibration coefficients for the NOAA-17 satellite developed by NOAA after the 2004 growing season. Images available below from the 2004 - 2009 growing seasons reflect the updated calibration coefficients. In February 2012, the AVHRR NOAA-17 sensor began having scan motor problems that affected data quality. Effective March 2012, NOAA-18 will be the new vegetative condition monitoring satellite. Animations of these images for a given year reveal how the vegetation condition changed during that growing season.


Select a 2012 Biweekly Period to View


Last Modified: 04/09/2012