River breeze circulation in eastern Amazonia: observations and modelling results

The CIRSAN/LBA field campaign was conducted close to two major rivers of the Amazon Basin, the Tapajos and the Amazon. The observations indicate that during weak trade wind episodes the Tapajos River breeze actually induces a westerly flow at the eastern margin with an associated line of shallow cumulus. The atmospheric circulation induced by the river has been interpreted with the help of a high resolution numerical simulation. A single cell forms during late morning over the Tapajos River and evolves into the afternoon with ascending motion in the eastern margin and a descending branch in the western margin suppressing cloud formation. During the night, convergence is seen along the centre of the River Tapajos. The implications of the particular geometry of the river with respect to the trade winds for the generalization of the surface measurements of turbulent fluxes of heat, moisture and CO2 in the Tapajos eastern margin of the Amazon Basin as a whole are discussed.