Nonextensivity in atmospheric surface layer turbulence

We present a statistical modelling of wind velocity increments for turbulent data measured in the atmospheric surface layer above the Amazonian forest, in a micrometeorological tower built at the Amazonian Forest Rebio-Jaru Reserve (10 04' S; 61 56' W) during the LBA (Large Scale Biosphere Atmosphere in Amazonia) wet season campaign. The data were measured by a 3D Campbell sonic anemometer at a sampling rate of 60 Hz and at a height of 67 m (the forest canopy has a mean height of 35 m; howover, some of the higher tree branches have a height of 45 m). . The goal of this investigation is to detect non extensivity property of the turbulent field in such a peculiar environment. To do this we calculate the probability density function (PDF) for wind velocity increments Vr(x)=V(x)-V(x+r) at different length scales r. The preliminary results show some evidence that the nonextensive thermostatistics modelling proposed by Tsallis [1] provides a new and simple framework for explaining the statistical behavior of fully developed turbulence. We also to investigate the relationship between intermittency and nonextensivity by means of one single parameter q, from Tsallis thermostatistics.

1. Tsallis, C. Possible generalization of Boltzmann-Gibbs statistics. Journal of Statistical Physics,v. 52, n. 1-2, 1988.