Estrutura vertical e relações de similaridade da velocidade do vento na subcamada rugosa sobre coberturas de vegetação densa

Abstract

The roughness sublayer (RSL) is a region within the surface boundary layer (SBL) where the turbulence behavior differs from predictions made by the Monin-Obukhov similarity theory (MOST), located near or within surface roughness elements, such as trees, buildings and other obstacles. Most measurements performed in forested areas, such as the Amazon rainforest, occur within the RSL, but there is still no widely accepted theory to describe its behavior, and its basic characteristics are poorly understood. This study aims to estimate the RSL height (z∗ ) using three methodologies existing in the literature De Bruin and Moore (1985), Verhoef (1997) and Kuparinen (2007) and to propose a new formulation based on dimensionless profiles more compatible with turbulent flow over the Amazon rainforest canopy. The scales considered in this analysis include the wind shear length scale (Ls ), the height of the inflection point in the vertical wind profile (zi ), and the wind speed at that point (ui ), obtained from data obtained from sonic anemometers installed on the towers of the ATTO (Amazon Tall Tower Observatory) project. In the method of De Bruin and Moore, the mean height of the RSL was 56 m, in that of Verhoef (1997) 55 m, and in that of Kuparinen it was 64 m. From the organization of the Ls, zi and ui scales, the relationship z∗ = zi + 2Ls was proposed, resulting in an average RSL height of 87 m, a more realistic value, considering the assumption that the RSL height is between 2 and 3h (with h = 35 m being the canopy height in ATTO), as advocated by several authors. In addition to allowing the calculation of the RSL height, such scales can be used as normalization factors for physical quantities such as length and velocity scales. It was observed that the turbulent profiles normalized by Ls, zi and ui presented statistical errors (correlation and standard error, for example) considerably smaller than the profiles normalized by classical parameters such as friction velocity (u∗ ) and h, which can contribute to obtaining more realistic parameterizations of the turbulent exchange processes within and above the Amazon forest canopy.