Parameter Tree:
EARTH SCIENCE > LAND SURFACE > LAND USE/LAND COVER > LAND USE/LAND COVER CLASSIFICATION > VEGETATION INDEX

Definition:
An index that is determined using visible and near-IR channels on AVHRR. Denotes relative chlorophyll content of vegetation during daylight conditions, and is thus used to monitor drought conditions.

Reference:
National Weather Association (NWA) Remote Sensing Committee