Abstract
This research presents an analysis of the frequencies and vibration modes of the structure of the superficial seiches of Lake Chapala using mathematical modelling and measurements. The HAMSOM model was run with wind fields from coastal meteorological stations and for different lake storage levels. The lake water level measurements were carried out in two campaigns in 2003. An analysis of the surface seiches in the lake was performed using the fast Fourier transform method. A spectral analysis of lake water level measurements reveals seiches with periods close to 5.9, 3, 2, and 1.5 h. A comparison with the periods calculated by the HAMSOM model indicates that these periods correspond to superficial seiches of the fundamental longitudinal mode of the lake and the subsequent three modes. The lake has undergone important changes in its storage level over time. Therefore, we modelled it with storage levels from the isobaths 90 to 95 m and found that surface seiche periods decreased to 5.2 h.
Highlights
In Lake Chapala and other closed or semi-closed water bodies, there are gravitational waves that have greater frequency and lower amplitude, these are generated by different mechanisms that promote natural resonant oscillations known as seiches
Lake-level measurements during the two campaigns are shown in Fig. 2, and these measurements may have high uncertainty due to contamination of the data by frequency aliasing and nonseiche oscillations as well as by water inflow and outflow
The research results provide the spatial distribution of lake water level oscillations for seiche periods
Summary
In Lake Chapala and other closed or semi-closed water bodies, there are gravitational waves that have greater frequency and lower amplitude, these are generated by different mechanisms that promote natural resonant oscillations known as seiches (own oscillations). Recent studies have shown the existence of long waves, derived from the non-linear interaction of waves and wind waves (infragravity waves) These waves lead to phenomena in surf and coastal zones, such as: water currents, waves shape, crescent bars, beach tops and other forms produced by coastal topography, as sediments by trawling materials[1,2]. Non-linear interactions and atmospheric processes such as wind and waves, are the commonly factors that induce oscillations in water bodies. Free periodic oscillations or normal modes, are generated when the winds suddenly stop over a lake, whereby the inclined surface produced by the accumulation of water tends to establish a static equilibrium. Et al.[12] showed that the process varies over time, as the energy dissipates as the root mean square wave height decreases when the wave breaks. Free oscillations or seiches in lakes have been studied over time, and such research has been carried out through the use of vertically integrated models and in situ measurements, such as in Lake Geneva[13], www.nature.com/scientificreports/
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