Observed Influence of Vegetation Variability and Change on the Climate of South America

Land surface variability and change can affect the overlying atmosphere through biogeophysical and biogeochemical feedbacks. The goal of our work is to quantify the local and remote influences of vegetation on the climate of South America using observational records. We first analyze the spatio-temporal variability of vegetation over South America, with a special focus on the La Plata River basin. The analysis uses a 34-year (1981-2014) record of modified Enhanced Vegetation Index (EVI2) from the Vegetation Index and Phenology (VIP) datasets of the NASA MEaSUREs project, in addition to 17-year (2000-2016) remotely sensed Enhanced Vegetation Index (EVI) data derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Terra satellite. The dominant patterns of variability in space and time are analyzed using empirical orthogonal function/principal component (EOF/PC) analysis on a basin-wide scale. The dominant modes can be attributed to anthropogenic deforestation using observational records of land use change from the History Database of the Global Environment (HYDE), and to natural causes using observed records of terrestrial surface temperature and precipitation provided by the University of Delaware. The second part of the study analyzes how these dominant modes of variability affect the overlying atmosphere at the continental scale. We use generalized equilibrium feedback assessment (GEFA) to statistically quantify the observed seasonal impacts of dominant terrestrial and oceanic forcings on the South American climate.