Interrelated Changes of Wind Profile Structure and Richardson Number in Air Flow from Land to Inland Lakes

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  • 1 University of Wisconsin, Madison
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Abstract

A semi-empirical model for wind profile modification, in airflow from land to water on the 2-km scale, is discussed using 1950 Lake Hefner data. Initial (rough-surface) and final (smooth-surface) profiles are derived and an interpolation model is developed and used to calculate intermediate profiles. A distribution of vertical velocity with height is determined with the aid of the assumption that the divergence in the x direction near the surface is compensated by convergence in the y direction aloft. The rate of growth of the internal boundary layer follows as a direct consequence of the model. Theoretical computation is compared to Super's observations of wind profile variations with fetch on Lake Mendota. A diurnal variation of subsidence found over Lake Hefner is related to the variation in thermal stratification and its effect on the wind profile structure. Momentum budgets between land and lake are constructed and give evidence of a diurnal variation in surface stress over Lake Hefner.

Abstract

A semi-empirical model for wind profile modification, in airflow from land to water on the 2-km scale, is discussed using 1950 Lake Hefner data. Initial (rough-surface) and final (smooth-surface) profiles are derived and an interpolation model is developed and used to calculate intermediate profiles. A distribution of vertical velocity with height is determined with the aid of the assumption that the divergence in the x direction near the surface is compensated by convergence in the y direction aloft. The rate of growth of the internal boundary layer follows as a direct consequence of the model. Theoretical computation is compared to Super's observations of wind profile variations with fetch on Lake Mendota. A diurnal variation of subsidence found over Lake Hefner is related to the variation in thermal stratification and its effect on the wind profile structure. Momentum budgets between land and lake are constructed and give evidence of a diurnal variation in surface stress over Lake Hefner.

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