Characteristics and variability of the Atmospheric Water Balance of the Amazon Basin

The water balance of the Amazon basin is of great importance, due to the presence of the world’s larges hydrographic system. Hence, there is a concern that large-scale land use changes may change significantly the flow regimes of rivers within the region and the land-atmosphere exchange of moisture, as well as the moisture fluxes from the basin to other regions of South America. This paper describes a research effort to estimate the atmospheric water balance of the Amazon basin, as a whole and by regions, using the NCEP reanalysis, and the network of river and rainfall data in the region.

Quantifications are made for the near-surface moisture input from the North Atlantic into the Northern Amazon, from the Northern Amazon into the southern part of the basin, and from the basin to adjacent regions outside the basin, suchas central and Southern Brazil-Northern Argentina-Southern Brazil. In additions, annual, interannual and decadal variability of the water balance and its terms are studied, in relation to issues such as the ENSO phenomenon, the Atlantic SST dipole, and the decadal variability that have been previously identified in the Atlantic sector of South America. Preliminary results indicate the presence of decadal variability in rainfall and moisture transport especially in the northern parts of the basin, the effects of ENSO, and a long-term trend that seems to be due to both natural and human induced climate variability.