CLIMATE MONITORING USING AN AVHRR-BASED VEGETATION INDEX

A normalized difference vegetation index (NDVI) has been produced and archived on a 1-degree latitude by 1-degree longitude grid between 55-degrees-S and 75-degrees-N. There are many sources of data errors in the NDVI including cloud contamination, scan angle biases, changes in solar zenith angle, and sensor degradation. Week-to-week variability is primarily caused by cloud contamination and scan angle biases and can be minimized by temporally filtering the data. Orbital drift and sensor degradation introduces interannual variability into the dataset. These trends make the usefulness of a long-term climatology uncertain and limit the usefulness of the NDVI. Elimination of these problems should produce an index that can be used for climate monitoring.