Estudo da Variabilidade Noturna dos Ventos em Regiões Tropicais

Abstract

The characteristics of the vertical structure of the atmosphere near the surface influence the physical, biotic and anthropic environments, because it is in this region that the incident solar energy is redistributed, part of it being reflected, part stored and another part used to transport heat and water vapor into the atmosphere via turbulent processes that occur in the region located just above the surface, the atmospheric boundary layer (ALC). Of particular interest are the nighttime atmospheric boundary layer (NLL) phenomena, where the flows are associated with various physical processes that introduce additional difficulties in parameterizing the exchange processes. Many of the exchange phenomena between surface and atmosphere and many of the evolution characteristics of the CLN are still poorly understood, including above the Amazon Rainforest. For this reason, this work seeks to study the evolution of CLN, from its evening transition, following the methodology proposed by Cava et al. (2004), by which classes of variability patterns of CLN quantities are defined and in which nighttime data of wind speed (v), radiation balance (Rn), carbon dioxide concentration (c), specific humidity (q) and temperature (T) are investigated, amassed at sufficiently high rates. In this study, the data used were measured above the Caxiuanã National Forest, in a 54 m high meteorological tower, between the months of March and December 2005. It was possible to establish the percentage of occurrence of the various classes that express patterns of variability of nocturnal runoff. The data from the Caxiuanã Forest indicates the presence of organized movement in the form of coherent structures during almost all the cases investigated. The results show that in the periods studied (more than 90% of the cases) there was organized turbulence in structures in the form of ramps for the scalars. Episodes with considerable variations in the radiation balance (greater than 10 W/m2 ) corresponded to about 70% of the cases. These results differ from those found in other meteorological towers in the Amazon Rainforest and suggest the existence of important local mechanisms generating turbulent kinetic energy during almost the entire night.