Zero-crossing statistics, although not widely known, could play an important role in he analysis of turbulence. In this thesis, the turbulence structure and turbulent scales in the Atmospheric Boundary Layers were studied using zero-crossings statistics related to fluctuating velocity time series obtained from measurements. Within this thesis measurement data from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition has been analyzed. The main focus of this
expedition was to investigate the stably stratified surface layers, where turbulence may become intermittent, i.e. it may locally cease to exist, such that the flow relaminarises.
The zero-crossing statistics were calculated first for artificially created
laminar-turbulent signals. It was shown that the ratio of two scales, Taylor length scale, related to turbulence eddies, and the Liepmann scale, related to zero-crossing statistics, can be used as a measure of the flow intermittency. Next, time series from the measurements were investigated and it was shown that the corresponding intermittency parameter depends on the level of the stratification.