Temperature auto-correlation and spectra functions in low-wind meandering conditions

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 auto-correlation functions, suggests that a dynamical link between temperature and velocity oscillations exists.