NDVI Vegetation Archive

TMAI has an extensive archive of NOAA AVHRR satellite imagery. The core of this data base is an eleven year (1989 - 2000) collection of bi-weekly NDVI composites created by EROS to minimize the amount of cloud cover. The NDVI data set covers the entire conterminous US, however we are able to subset specific regions (corn and wheat belt, State, CRD, county) for more detailed analysis.

VPM Dataset

Using the eleven year NDVI dataset for the US, Vegetation Phenology Metrics (VPM) are calculated to identify the date and NDVI value associated with specific vegetative growth stages.

Metrics that make up the database include:

Onset of greenness

Time at which vegetation begins active growth and photosynthesis

Maximum greenness

The time when the NDVI reaches its maximum, and its associated date

End of greenness

The date at which the NDVI values return to the level at which onset occurred

Growing season

The length of time between onset date and end date

Growing days

The length of time between onset date and maximum NDVI

Rate of green-up

The difference in NDVI between onset and maximum divided by growing days

Accumulated NDVI

 Metrics Used to Monitor Vegetation
with AVHRR Data

Vegetation Curve and Associated Vegetation Phenology Metrics(VPM)

Vegetation Phenology For Corn in Kansas
A Visual and Spectral Analysis

The spectral curve above illustrates the stages of corn development through the 1999 growing season within a field in eastern Kansas. Notice the rapid increase in greenness (plant-biomass) after the onset date, and the slight decrease after tasseling. These fine details are obtained from satellite data for the entire United States and can be used to monitor vegetation health and determine crop yields.

Onset of Greenness Date is highly associated with the length-of-season and crop yields,
and is just one of the vegetation metrics used to monitor vegetation condition and change.