Examining vegetation phenological change in South America using reconstructed SeaWinds data: grasslands and savanna

This research reports the use of NASA SeaWinds data to measure phenological change in equatorial South America through a growing season. The SeaWinds data was reconstructed to a resolution of 8 km and studied on a monthly basis. Vertically and horizontally polarized data were examined in the context of monthly NDVI composites as well as monthly weather variables. Thirty-nine vegetation physiognomic classes and transition types were studied using data collected in the year 2000. Only the preliminary results for equatorial savannas of northern South America are discussed in this paper. Backscatter in these savannas is correlated primarily with NDVI and precipitation totals. Backscatter difference (HH - VV) is likewise very strongly correlated with monthly precipitation. We hypothesize that backscatter from the top of the canopy and multiple-bounce backscatter from wet soils are the key components explaining seasonal SeaWinds backscatter change within this class.