NDVI Intercalibration of AVHRR, SPOT Vegetation and MODIS

We have intercalibrated the NDVI time series of the AVHRR instruments with moderate- and coarse-resolution NDVI data from SPOT Vegetation and the MODIS instrument on Terra. Benefits of this include using longer time series means to calculate anomalies, being able to use SPOT Vegetation and MODIS Terra NDVI data quantitatively with respect to a 25-year NDVI record, and having multiple NDVI data sources in case one or more satellites or instruments fail. Here we present the results of the NDVI intercalibration using NDVI from the AVHRR instruments at 8 km, SPOT Vegetation at 1 km and a 16 day and monthly Terra MODIS dataset at 1 and 5 km. A description of a new AVHRR NDVI 1981-2004 data set and its intercalibration with SPOT Vegetation are also presented. Fourteen of the CEOS Land Validation core sites were used in conjunction with eight drought hotspots from around the world to evaluate the ability of all three sensors to detect variations during their periods of record. Analysis and statistics of time series, correlation among datasets, measures of autocorrelation, and an analysis of anomaly images using AVHRR means will be presented.