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In this study, sonic anemometry measurements at 16 vertical levels of the ATTO tower were used to evaluate the temporal variation of the multiresolution (co)spectra of the wind speed and temperature components. This methodology made it possible to visualize, over a large vertical extent, which scales of turbulent movement contribute most to turbulent kinetic energy and turbulent transport of a quantity over the Amazon rainforest. In this respect, it was also possible to identify the turbulent scales most effective in the entrainment process in the early morning. The multiresolution analysis also highlighted the need to determine the scale of the spectral gap in order to obtain more robust estimates of turbulent fluxes, even for the daytime period. [ABSTRACT FROM AUTHOR]

Mixing length was introduced in the early 20th century to determine turbulent viscosity. Since then, various formulations have emerged, reflecting the complexity of parameterizing turbulent fluxes, especially under strongly stable conditions. This study proposes a new mixing length formulation based on the dissipation of turbulent kinetic energy, avoiding autocorrelation issues. Results show the new formulation behaves consistently, decreasing with stability in weakly stable conditions and increasing in strongly stable conditions. Comparisons with other formulations indicate that this approach offers a more robust description of turbulence in the stable boundary layer (SBL). [ABSTRACT FROM AUTHOR]

The Atmospheric Boundary Layer (ABL) is the portion of the lower troposphere that interacts with and is influenced by the Earth's surface. It is a key parameter for micrometeorology, atmospheric chemistry, and other fields of study. However, estimating the height of the nocturnal boundary layer (NBL) is not trivial, and the techniques used so far have never estimated the top of the NBL with turbulent flux profiles (the most appropiate technique for this purpose). This work proposes an innovative methodology for calculating the height of the NBL, using data from 13 three-dimensional sonic anemometers installed on the towers of the ATTO experimental site, located in the central Amazon. Two days were used, one characteristic of the rainy season and the other of the dry season. The results showed that the flux convergence methodology is promising for determining the NBL height. It was observed that, during the dry season, the heights were lower (average of 86.60 m) compared to the rainy season (average of 160.42 m). The higher heights during the rainy season can be attributed to the greater presence of clouds during this period, resulting in a higher amount of longwave radiation emitted by these clouds. This influences the increase in turbulence due to the available radiative balance and, consequently, resulting in higher NBL heights. These results will be further explored with the use of a larger dataset. [ABSTRACT FROM AUTHOR]

Extreme heat events have been reported more frequently in recent years. However, few studies have addressed the effects of theseevents on turbulent fluxes in the atmospheric boundary layer. The objective of this study is to investigate the anomalous behavior of sensible and latent heat fluxes and their relationship with extreme heat events in a wheat crop in the municipality of Carazinho-RSduring winter. The analysis showed a relationship between the intense advection of warm air from the northern quadrant with the increase of latent heat flux and consecutive days in which the sensible heat flux remains negative. Therefore, the extreme heat event significantly alters the expected pattern for the behavior of near-surface fluxes. [ABSTRACT FROM AUTHOR]

In this work, an investigation of the influence of topography on the structure of the turbulence of the Amazon rainforest is carried out. To better understand how topography acts in the organization of turbulence, in turbulent fluxes of energy and mass, inside and above the forest canopy, the Parallelized Large-Eddy Simulation Model (PALM) was used. The model's input dataset comes from the ATTO site (Amazon Tall Tower Observatory) between October and November 2015. From these measurements, from different heights, two simulations were performed for the daytime period: with topography and without topography. In both simulations, the U/Uh profile shows that the wind becomes weaker as it bumps into the forest canopy, leading to an inflection point in the wind profiles. In addition, the simulation with topography induced ascending and descending movements, which affected the concentration of the passive scalar. Finally, the topography impacted the turbulence intensity. [ABSTRACT FROM AUTHOR]