The Amazon basin is the planet’s largest and most intense land-based centre of precipitation. This convective system is driven by high net surface radiation, which is dissipated via fluxes of latent heat and sensible heat. Over the long term (1 year or greater), incoming precipitation over the basin is balanced by evaporative fluxes of water to the atmosphere and discharge, which returns excess water to the oceans. The temporal variability of this cycle is largely controlled by oscillations of tropical Pacific and North Atlantic sea surface temperatures, while synergies between climate and forest structure and functioning control much of the observed spatial variability.
Field observations and numerical models indicate that large-scale deforestation has decreased net surface radiation and evapotranspiration, increasing sensible heat flux, water yield, and stream discharge in many locations, particularly in the agricultural frontier of southeastern Amazonia. In the future, increasing atmospheric greenhouse gases are expected to increase temperatures, drought frequency, and drought intensity in the Amazon, causing further changes to the cycling of energy and water in the basin.
