Detection of Mesoscale Seasonal and Inter-annual Variation In Vegetation of the Amazon Basin
Victoria
Ramos
Ballester, CENA-USP, vicky@cena.usp.br
(Presenting)
Miles
G
Logsdon, University of Washington,, mlog@u.washington.edu
Milton
Smith, University of Washington, msmith@u.washington.edu
Robin
Weeks, University of Washington, rweeks@u.washington.edu
Reynaldo
Luiz
Victória, CENA-USP, reyna@cena.usp.br
Jeffrey
E.
Richey, University of Washington, jrichey@u.washington.edu
In the Amazon Basin, seasonal and inter-annual spectral changes measured by satellites result from anthropogenic disturbance and from the interaction between climate variation, and the ground and vegetation cover. Measurements of spectral change provide information on physical processes controlling this interaction at the mesoscale. In this article we analyze a 17-year sequence of daily AVHRR-GAC images to produce a monthly record of surface spectral change encompassing El Niño Southern Oscillation (ENSO) cycles. Monthly cloud free composite images from daily AVHRR data were produced by linear filters that minimize the fine scale spatial variance and allowed for a wide range analysis within a consistent mathematical framework. We report here on the use of a minimized local variance filter (MLV) that produced spatially smooth images in which major land cover boundaries and spatial gradients are clearly represented. Changes in the configuration of these boundaries and the composition of the elements they defined are described in terms of landscape change. The time series produced with the MLV filter reveals a marked seasonal difference in the pattern of the landscape and structural differences over the length of the time series. Strikingly, the response of the region to drier El Niño years appears to be delayed in the MLV series, the maximum response being in the year following El Niño and little or no change seen during El Niño.
Submetido por Maria Victoria Ramos Ballester em 18-MAR-2004
Tema Científico do LBA: LC (Mudanças dos Usos da Terra e da Vegetação)