Abstract ID: 153

Low level jets and intermittent turbulent events in the Nocturnal Boundary Layer above the Amazon Rain Forest

The nocturnal boundary layer (NBL) presents many features to be explained. Previous studies have showed the occurrence of nocturnal intermittent turbulent phenomena in this layer of the atmosphere. The comprehension of such phenomena becomes more important above the forest environment, where they are usually associated to alterations in the forest-atmosphere exchange regimes. An important phenomenon of the NBL is the low level jet (LLJ), which induces turbulent mixture in the region where it occurs and, possibly, at the surface. These jets have already been detected above the Amazon Rain Forest and seem to be related to local breeze circulations. Moreover, some researches in other forested regions have concluded that the jet's intermittent activity influenced the carbon dioxide exchange. This demonstrates the jets importance over the nocturnal fluxes and the forest-atmosphere coupling. The LLJs may also be associated to intermittent turbulent events at the forest surface, such as wind gusts and gravity waves. Recently, the relation between shear conditions associated to the jet and the occurrence of global intermittency has been studied. This work has investigated the relation between the occurrence of low level jets above the National Forest of Caxiuanã (Oriental Amazonia) and wind gusts at the surface, during some nights of its dry season (COBRA-PARÁ Experiment), considering the local shear and the existence of gravity waves, to contribute for the comprehension of the physical mechanisms associated to these phenomena, particularly the strong shear that may prevent that gusts and jets occur simultaneously.

Session:  Carbon - What has been learned and what further can be learned from a network of eddy covariance towers in Amazonia?.

Presentation Type:  Oral