Beating of the Amazon: Visualizing the Diurnal Cycle of the Amazonian Hydroclimatology

The Amazon rainforest is the largest and most biologically diverse ecosystem in the planet. Moisture-laden tropical winds from the Atlantic Ocean enter the Amazon, bringing precipitation to the forest; the dense canopy then then transpires and contributes water for precipitation downwind. In fact, it has been estimated that between 20% and 40% of Amazonian rain comes from transpiration and evaporation (ET) from the forest itself. However, only recently have we been able to quantify the contribution of Amazonian ET to precipitation. Using the state-of-the art Weather Research and Forecast (WRF) atmospheric model with water tracers, we are able to trace the moisture that originates from the Amazon rainforest. This is analogous to putting dye in the model’s hydrologic cycle. By visualizing the output of this model we were able to show, for the first time, that the diurnal cycle of transpiration provides a clear diurnal signal to the overlying atmospheric water vapor and can be visualized as a “beating” over the Amazon. The rain and the winds also have a clear diurnal cycle, and shows how the land’s signature can be seen in the hydroclimatology above.