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Modelling the thermal regime of a lake during the winter season
AbstractThe thermal regime of a lake is investigated using both measured and numerically simulated data. The temperature measurements clearly demonstrate the importance of knowing the amount of short wave radiation that penetrates the ice-cover and the sediment heat flux from the lake bottom. However, the sediment/water coupling will not be treated in this study. In the numerical simulations a one-dimensional model is used, where the vertical exchange coefficient is calculated by a two-equation turbulence model. The meteorological forcing, which enters the model through the surface boundary conditions, is calculated on the basis of synoptic meterological observations every third hour. These boundary conditions are strongly affected by ice formation at the surface. Therefore, parameterizations of the initial ice formation and break-up and the ice growth and melting are included in the model. The amount of short wave radiation that reaches the ice/water interface is modelled in the following three steps: first, there is the snow or ice surface albedo, second, an absorption occurs in the upper 0.1 m of the ice and/or snow-cover, and third, the remaining radiation decays exponentially down to the ice/water interface.The modelled initial ice formation and break-up together with the ice growth and melting are verified against measurements with satisfactory results. Also the calculated water temperature increase and its vertical structure are well described by the model.
Modelling the thermal regime of a lake during the winter season
AbstractThe thermal regime of a lake is investigated using both measured and numerically simulated data. The temperature measurements clearly demonstrate the importance of knowing the amount of short wave radiation that penetrates the ice-cover and the sediment heat flux from the lake bottom. However, the sediment/water coupling will not be treated in this study. In the numerical simulations a one-dimensional model is used, where the vertical exchange coefficient is calculated by a two-equation turbulence model. The meteorological forcing, which enters the model through the surface boundary conditions, is calculated on the basis of synoptic meterological observations every third hour. These boundary conditions are strongly affected by ice formation at the surface. Therefore, parameterizations of the initial ice formation and break-up and the ice growth and melting are included in the model. The amount of short wave radiation that reaches the ice/water interface is modelled in the following three steps: first, there is the snow or ice surface albedo, second, an absorption occurs in the upper 0.1 m of the ice and/or snow-cover, and third, the remaining radiation decays exponentially down to the ice/water interface.The modelled initial ice formation and break-up together with the ice growth and melting are verified against measurements with satisfactory results. Also the calculated water temperature increase and its vertical structure are well described by the model.
Modelling the thermal regime of a lake during the winter season
Sahlberg, Jörgen (author)
Cold Regions, Science and Technology ; 15 ; 151-159
1988-02-02
9 pages
Article (Journal)
Electronic Resource
English
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