MODELING GASEOUS DRY DEPOSITION OVER REGIONAL SCALES WITH SATELLITE-OBSERVATIONS .2. DERIVING SURFACE CONDUCTANCES FROM AVHRR DATA

This paper describes methods to couple the reflectance-resistance model developed in Paper I with the normalized difference vegetation index (NDVI) data from the advanced very high resolution radiometer (AVHRR) on satellites over the eastern United States. A land use data set was also employed to determine appropriate model parameters suitable for describing differences in characteristics of light scattering and leaf resistance among different plant canopies, especially between forests and short canopies (crop and grass, etc.). As a case study, the biweekly averaged NVDI data for a year with normal precipitation (1987) and a drought year (1988) were selected for analysis to maximize differences in vegetative conditions and canopy conductance for pollutant transfer. The satellite-derived NDVI over the region had a much lower value in summer 1988 than in summer 1987. The depression was especially large for cultivated areas and rangelands, but it was much less significant for forested regions. The NDVI data were incorporated into the model to calculate the regional distribution of canopy conductances for pollutant transfer to the earth's surface.