AVHRR TEMPORAL ANALYSIS OF A SAVANNA SITE IN BRAZIL

This work investigated the temporal monitoring of savanna ('cerrado') vegetation phenology in the Emas National Park of Brazil utilizing 1.1 km full resolution daily images of the Advanced Very High Resolution Radiometer (AVHRR) on-board the NOAA-11 satellite. For a period of 18 months studied in 1992-93, only 26 images had useful data. Digital ana lysis of individual images concentrated on five sub-areas of up to 30 km(2) each. Channels used were 1 (0.6-0.7 mu m), 2 (0.7-1.1 mu m) and 3 (3.5-3.9 mu m), as well as the Vegetation Index (NDVI) which combine s channels 1 and 2. A high resolution Thematic Mapper (TM) Landsat ima ge and field work provided ground data to identify the vegetation type s. Channel 3 and NDVI showed the strongest temporal response to phenol ogical changes of the vegetation, while channels 1 and 2 presented hig h dependence on the off-nadir scan angle. The results indicated large variations in the daily AVHRR signal of channels 1 and 2 for the same area, regardless of vegetation changes. Regular monitoring of the 2 x 10(6) km(2) of Brazilian cerrados using AVHRR full 1.1 km resolution i s recommended, particularly with the 3.7 mu m band.