Internal wave weather heterogeneity in a deep multi-basin subalpine lake resulting from wavelet transform and numerical analysis

- We investigated the internal wave field in a deep Y-shaped south alpine lake.
- The study included both wavelet analysis and numerical modeling.
- We analyzed temperature and wind data collected over three years in three lake points.
- We identified first and second vertical wave modes, the first active even in winter.
- Oscillations in one lake arm resulted decoupled from the rest of the lake.

The internal wave-field of a Y-shaped lake (Lake Como, North Italy) was investigated over a 3-year long period applying wavelet time-frequency analysis to temperature and wind data time series, recorded at the edge of each of the three arms. The comparison with the results from a modal model allowed to identify the presence of both first and second vertical modes of oscillations. The field data analysis underlined a heterogeneous baroclinic response with the eastern arm decoupled from the remaining part of the lake constituted by the northern and western arms (north-south west transect). This disjoined response is expected to enhance the water exchange between the northern and the western arm, with relevant consequences on the inter-basins water exchanges and on the distribution of chemical and biological species. In the north-south west transect the analysis of the low power signals in winter underlined a residual internal wave activity ascribed to the first vertical free mode of oscillation (V1H1).