AVHRR temporal analysis of a savanna site in Brazil

Abstract. 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 analysis of individual images concentrated on ®ve sub-areas of up to 30 km2 each. Channels used were 1 (0.6±0.7 mm), 2 (0.7±1.1 mm) and 3 (3.5±3.9 mm), as well as the Vegetation Index (NDVI) which combines channels 1 and 2. A high resolution Thematic Mapper (TM) Landsat image and ®eld work provided ground data to identify the vegeta-tion types. Channel 3 and NDVI showed the strongest temporal response to phenological changes of the vegetation, while channels 1 and 2 presented high dependence on the o-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 2Ö106 km2 of Brazilian cerrados using AVHRR full 1.1 km resolution is recommended, particularly with the 3.7 mm band. 1