The seasonal evolution of high vertical–mode internal waves in a deep reservoir
Full Text
Share
The causal mechanism and seasonal evolution of the internal wave field in a deep, warm, monomictic reservoir
are examined through the analysis of field observations and numerical techniques. The study period extends from
the onset of thermal stratification in the spring until midsummer in 2005. During this time, wind forcing was
periodic, with a period of 24 h (typical of land–sea breezes), and the thermal structure in the lake was
characterized by the presence of a shallow surface layer overlying a thick metalimnion, typical of small to medium
sized reservoirs with deep outtakes. Basin-scale internal seiches of high vertical mode (ranging from mode V3 to
V5) were observed in the metalimnion. The structure of the dominant modes of oscillation changed as
stratification evolved on seasonal timescales, but in all cases, their periods were close to that of the local wind
forcing (i.e., 24 h), suggesting a resonant response. Nonresonant oscillatory modes of type V1 and V2 became
dominant after large frontal events, which disrupted the diurnal periodicity of the wind forcing
Tots els drets reservats