A comparison between Terra MODIS and NOAA AVHRR NDVI satellite image composites for the monitoring of natural grassland conditions in Alberta, Canada

Natural grasslands in Alberta are largely used for cattle grazing operations. The abundance of this feeding source is largely subject to climate variability. Given the large area of grazing pasture and grasslands (almost 9 million hectares) and its value to the livestock industry in Alberta, it would be useful for both rangeland managers and governments if a pasture insurance program could be developed based on satellite imagery. Grazing pastures and grasslands were monitored throughout the province using satellite image data for 2002 and 2003. Normalized difference vegetation index (NDVI) composites derived from National Oceanic and Atmospheric Administration (NOAA) advanced very high resolution radiometer (AVHRR) and Terra moderate resolution imaging spectroradiometer (MODIS) sensors were used and compared with in situ, natural grassland productivity data. Overall, statistical correlation between NOAA AVHRR and Terra MODIS image composite data and the in situ field data yielded similar results, with correlation coefficients of 0.71 and 0.74, respectively. Additionally, the strong correlation of 0.87 between AVHRR and MODIS NDVI images indicates that MODIS NDVI data can be used as a complementary source of NDVI data and to populate the existing AVHRR historical database.