AN ASSESSMENT OF AVHRR NDVI-ECOCLIMATOLOGICAL RELATIONS IN NEBRASKA, USA/

Research designed to better define relations between 1-km multitempora l AVHRR-derived NDVI data and selected climatological parameters, soil hydrological properties and land cover characteristics is summarized. Bi-weekly maximum value composite NDVI data and concurrently measured meteorological data acquired in 1990 and 1991 for Nebraska were utili zed to study relations between NDVI and accumulated growing degree day s, soil temperature, precipitation and potential evapotranspiration. T emporal change in NDVI was found to be closely linked with the tempera ture regime. NDVI-precipitation and NDVI-potential evapotranspiration relations exhibited time lags, although the length of lag varied with land cover type, precipitation, and soil hydrologic properties. NDVI r esponse to precipitation was stronger in natural grasslands and grassl and/wet meadows than in areas of irrigated cropland and mixed crop/gra ss. NDVI-climate relations were strongest where vegetation was develop ed on soils with low root zone available water capacity and high perme ability. Relations derived by using NDVI values over 3 pixel by 3 pixe l windows showed little difference from those using single 1 km pixel. This may reflect both the relatively homogeneous land cover character istics of the study area and the effect of off-nadir viewing geometry on AVHRR data acquisition.