Partitioning the Amazonian Evapotranspiration in Their Contribution to Precipitation Over the La Plata Basin: A Numerical Modelling Study

Evapotranspiration from the Amazon Forest significantly contributes to rainfall over the La Plata Basin. This study aims to evaluate the influence of different components of Amazonian evapotranspiration on precipitation over the La Plata Basin, associated with the moisture transport by the Low-Level Jet east of the Andes and the South Atlantic Convergence Zone. Four experiments were conducted using the Eta regional climate model from 1998 to 2009. The Control Experiment is set up with the roots of Amazonian trees reaching 2 m deep. The Rootless Experiment is set up without roots in the Amazon Forest. The Deep Root Experiment is set up with the roots of Amazonian trees reaching 7.2 m deep. The Interception Experiment is set up without water storage in the tree canopies of the Amazon Forest. The results of this study show that the transpiration of Amazonian trees is much more important to mean precipitation over the La Plata Basin than interception by tree canopies. Moreover, the deep soil water storage in the southern and eastern portions of the Amazon Basin constitutes a source of moisture to mean rainfall over the La Plata Basin during the austral winter and spring seasons, which is mainly possible by the Low-Level Jet east of the Andes and the South Atlantic Convergence Zone, respectively. This study recommends that the deep soil water uptake by Amazonian tree roots be considered in weather and climate simulations over the La Plata Basin.