Eulerian low-wind temperature statistics are investigated through the analysis of sonic anemometer observations gathered in two experimental campaigns, the Urban Turbulent Project in Northern Italy and the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (Brazil). The observed auto-correlations and spectra functions are tested with the theoretical relationships previously proposed for the horizontal velocity components in low wind speed conditions. The comparison showed that the temperature field, similarly to the horizontal velocity field, presents a characteristic oscillatory behaviour with a distinct isolated spectrum peak frequency due to the wind meandering. The ratio between this frequency and the one associated to the horizontal velocity components is close to one. This, together with the similarity between the temperature and velocity spectra and autocorrelation functions, suggests that a dynamical link between temperature and velocity oscillations exists.

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h i g h l i g h t s• We propose a new mathematical expression to describe the meandering phenomenon.• We employ wind data measured in a nocturnal PBL to obtain experimental ACF. • The new ACF satisfactorily represents the negative lobes of the meandering phenomenon. a b s t r a c tIn this study a new mathematical expression to describe the observed meandering autocorrelation functions in low-wind speed is proposed. The analysis utilizes a large number of best fit curves to show that the proposed theoretical function well reproduces the general form and the negative lobes characterizing the experimental meandering autocorrelation function. Further, the good agreement of the measured autocorrelation curves with the proposed algebraic autocorrelation function allows to calculate the magnitudes of the meandering period and of the loop parameter. The results agree with the values presented and discussed in the literature. Therefore, the new formulation describing experimental meandering autocorrelation functions can be used to simulate the dispersion of contaminant during low wind episodes and to determine relevant meandering parameters.

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The Pampa‐2016 experimental campaign was performed in a typical Pampa lowland South American region. It consisted of both surface flux measurements (at 3 and 29 m) and a radiosonde launched every 3 h. The resulting meteorological observations allowed for the analysis of turbulent properties associated with both a stable and a convective boundary layer. The combined analysis of the surface data and vertical soundings has revealed some general characteristics of the atmospheric boundary layer for both the nocturnal stable conditions and the daytime convective environment. The continuous surface measurements showed that the nocturnal stable inversion, occurring in calm winds, is basically generated by the radiative cooling mechanism that is established after the late afternoon transition. The analysis of night‐time surface data also showed that, under stable conditions in the case of vanishing wind speed, the friction velocity has unrealistic values that are very close to zero. This situation is undesirable for numerical models that generally use this quantity as a lower boundary condition. The analysis of night‐time temperature profiles revealed two contrasting patterns in agreement with the classical classification of radiative night (a very stable boundary layer) and a turbulent night (a weakly stable boundary layer). In contrast, the analysis of the daytime temperature profiles provided an estimation of the convective time scale that is of the order of 10 min, in agreement with experimental values. A spectral analysis and the consequent estimation of the spectral peaks under unstable and stable conditions were in agreement with literature values.