| Popis: |
The relationships between the normalized difference vegetation index (NDVI) and surface environmental variables are studied across the Canadian landmass using data over a six year period (1982 to 1987). The NDVI images are 15 day composites over the growing season obtained from NOAA AVHRR Global Area Coverage data. Daily climatological surface data in combination with vegetation and soil characterization digital data sets are input into a multilayer soil water budget model to calculate daily amounts of potential evapotranspiration (PE), actual evapotranspiration (AE), and soil moisture. A preliminary study for the year 1986 addressing the above relationships was undertaken by Cihlar et al. (1991). In this study, the stability of the relationships and the effect of a wide range of climatic conditions are investigated. It is found that consistently over the 6 year period, seasonal NDVI trajectories followed PE trends (and AE where water supply was not limiting), lagging by approximately one composi... |
