Bachelor thesis
Taylor’s hypothesis and the random sweeping effects in the stable atmospheric boundary layer. Analysis of data from MOSAiC expedition. |
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Author:Supervisor:Supervising institution:Year: |
Aleksandra KujawskaMarta WacławczykWydział Fizyki2025 |
This work investigates Taylor’s hypothesis and random sweeping effects in the stable atmospheric boundary layer, using experimental data collected during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition (Nixdorf et al., 2021). It focuses on the spectral description of turbulence. Subsequently, one-dimensional spectra, as well as the turbulence intensity parameter I, were calculated from tower-measured velocity time series. For this purpose, the Welch method was implemented in Python. This study confirmed that the obtained energy spectra generally follow the expected power law scaling, with some exceptions where distinct peaks suggest influences of local unsteadiness, gravity waves or flow transitions. Furthermore, after identifying the inertial range, linear fits were performed, from which the turbulent kinetic energy dissipation rate ϵ parameters were estimated and sensor-related effects observed. For these effects theoretical explanations were proposed. The impact of sensor-related effects on the spectra was modelled using a simple PAO-type function, which was shown to improve the agreement between measured and modelled spectra, thereby offering a framework for better interpretation of spectral distortions in observational data caused by sensor-related effects. Nondimensional wavenumber-dependent spectra was calculated and plotted in order to compare the experimental results to simulated ones from (Schr¨oder et al., 2024). Spectra showed partial consistency, providing moderate, though not conclusive, support for their results.
