Abstract
The spatial representativeness of anemometric tower measurements and the underlying hypothesis of horizontal homogeneity of the atmospheric flows have long being questioned in the literature. Further, forest are rarely situated on uniform and flat terrain in which the horizontally homogeneity of turbulence holds. The orography around the Amazon Tall Tower Observatory (ATTO) site makes no exception. The measurement site is located on a narrow plateau SW-NE oriented, surrounded by lower hills. It is then natural to investigate the spatial variability of the turbulent field around the ATTO and the INSTANT towers to understand the role played by gentle topography. The Parallelized Large-Eddy Simulation Model (PALM) is used to simulate the atmospheric flow over the Amazon Forest and to investigate the effect of topography on the Atmospheric flow within and above the roughness sublayer. The real topography of the ATTO site is considered, while a horizontally homogeneous leaf area density (LAD) profile is assumed for the canopy over the whole area. Hence, the flow variability can be totally ascribed to spatial orography gradients. The influence of orography is assessed comparing the profiles of the turbulent kinetic energy components and fluxes evaluate over flat terrain and over the real topography at different position on the horizontal plane. The dependence of the orography influence on the wind direction is investigated considering two different wind directions. 
Published Version
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