The STAR Vegetation Health Index is a product from NOAA's National Environmental Satellite, Data, and Information Service (NOAA-NESDIS) Global and Regional Vegetation Heath (VH) system estimating vegetation health, moisture condition, and thermal condition. VH products can be used as proxy data for monitoring vegetation health, drought, soil saturation, moisture and thermal conditions, fire risk, greenness of vegetation cover, vegetation fraction, leaf area index, start/end of the growing season, crop and pasture productivity, teleconnection with ENSO, desertification, mosquito-borne diseases, invasive species, ecological resources, land degradation, etc. The VH indices range from 0 to 100 characterizing changes in vegetation conditions from extremely poor (0) to excellent (100). Fair conditions are coded by green color (50), which changes to brown and red when conditions deteriorate and to blue when they improve. The VH reflects indirectly a combination of chlorophyll and moisture content in the vegetationhealth and also changes in thermal conditions at the surface.Monitoring vegetation health (condition), including drought detection and watch, is based on radiance measurements in the visible (VIS), near infrared (NIR), and 10.3-11.3 micrometers thermal (T) bands (channels) of the Advanced Very High Resolution Radiometer (AVHRR). These measurements are processed to reduce long-term noise. The VIS and NIR values were converted to the Normalized Difference Vegetation Index (NDVI=(NIR-VIS)/(NIR+VIS)) and the T to brightness temperature (BT) using a look-up table. The NDVI and BT were filtered in order to eliminate high frequency noise. They were also adjusted for a non-uniformity of the land surface due to climate and ecosystem differences using multi-year NDVI and BT data. The NDVI and BT were converted to the Vegetation Condition Index (VCI), Temperature Condition Index (TCI), and Vegetation Health Index (VHI).The Vegetation Health Index (VHI) is a proxy characterizing vegetation health or a combined estimation of moisture and thermal conditions.
AVHRR Vegetation Health Product - Vegetation Health Index
From September 1994 through February 1995, data were not available. Data and images displayed on STAR sites are provided for experimental use only and are not official operational NOAA products.
NOAA STAR Center for Satellite Applications and Research. 2018. Global Vegetation Health Products. Accessed through Resource Watch, (date). www.resourcewatch.org.