Organização da turbulência atmosférica na presença de uma linha de instabilidade acima de uma região florestada e desmatada na Amazônia

Abstract

Data from two experimental sites located in the State of Amazonas were used. These sites are part of the GoAmazon project, one of which is forested (ZF2) and the other is deforested (Manacapurú). In addition to the experimental data, radar and satellite images were also used to identify the presence of squall lines generated on the north coast of Brazil. Some of these lines have sufficient energy to move toward the state of Amazonas, passing above the ZF2 and Manacapurú sites. These lines that can move for long distances were called squall line type 2 (LIP2). It was found that 13 LIP2 passed above the Manacapurú and ZF2 sites during a period of 10 months. Due to the passage of these lines a drastic change was observed in the patterns of the organization of the atmospheric turbulence near the forested and deforested surface. One of them was chosen, because it is representative of the others, as a case study. It was observed that during the passage of LIP2 the following changes occurred: 1) significant drops in the equivalent potential temperature values, mainly in the forested region; 2) the average wind speed near the surface increases up to 6 times; 3) the skewness values of vertical wind velocity become considerably negative; 4) significant increases in turbulence intensity. All of these changes indicate the presence of strong downdrafts generated by LIP2. The strong downdrafts present during the passage of LIP2 above the experimental sites analyzed in this work may explain the increase in the concentration of ozone observed near the surface, that is, during the occurrence of the downdrafts, a portion of air, brought from top to bottom, rich In ozone makes the surface levels of ozone increase considerably. Another result that calls attention is the behavior of the sensible heat flux, calculated above and within the forest canopy. During the presence of LIP2 above ZF2 the values of the sensible heat flux above the forest canopy show opposite signs to the flux values inside the canopy. In addition, scaled analysis of the sensible heat flux, via multiresolution, showed that the temporal scale of the spectral peak for the period of LIP2 performance was approximately 5 times higher than during the period prior to LIP2. Finally, it was observed that the presence of LIP2 generates instabilities at the inflection point height on the wind profile. It was noted that during the LIP2 actuation the inflection point height approaches the top of the canopy. Analyzes of some terms of the turbulent kinetic energy balance (TKE) show that in the occasions of the presence of LIP2 the terms of shear production of TKE end dissipation rate of TKE are considerably larger when compared to the periods of absence of lines of instability.