Determination of seasonal and interannual variation in New Zealand pasture growth from NOAA-7 data

Abstract

The normalized vegetation index (NVI) has been calculated from afternoon overpasses of NOAA-7 for two important farming regions of New Zealand, approximately 1000 k 2 in area, for the period from October 1981 through June 1984. The uniform nature of the terrain and farming practices in these areas make them ideal targets for remote sensing from satellites with limited spatial resolution. The frequency of useful data coverage has been increased by sampling within cloud-free parts of a partly cloudy target area and also by deriving an empirical correction for off-nadir view angles. Daily area-mean rainfall and soil moisture were estimated for both regions and monthly area-mean pasture growth for one of them. The NVI was found to reflect the varying rainfall and soil moisture on time scales of one week or more during the growing season and between years. A correlation of 0.81 was found between NVI and pasture growth on a monthly mean basis. These results suggest that operational satellite monitoring of these and other areas would provide valuable assistance in agricultural management and forward planning.