Turbulent Kinetic Energy Budgets over Mountainous Terrain

Theodore S. Karacostas Department of Atmospheric Science, University of Wyoming, Laramie 82071

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John D. Marwitz Department of Atmospheric Science, University of Wyoming, Laramie 82071

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Abstract

The objective of this study is to describe the characteristics of the airflow and turbulence structure over mountainous terrain. Turbulent characteristics of the airflow were measured using well-instrumented aircraft. The shear, buoyancy, transport of energy and eddy dissipation rate terms were obtained from direct measurements. The turbulent kinetic energy budgets were determined with respect to height and horizontal distance upwind and downwind of the mountain. The change of turbulence intensity was also demonstrated by comparing power spectra as a function of height, as well as a function of distance upwind and downwind of the mountain. The results show that all measurable terms were significant. The shear production and the eddy dissipation rate were the dominant terms. The buoyancy and vertical transport terms were smaller but still important. The imbalance term was estimated to be relatively small.

Abstract

The objective of this study is to describe the characteristics of the airflow and turbulence structure over mountainous terrain. Turbulent characteristics of the airflow were measured using well-instrumented aircraft. The shear, buoyancy, transport of energy and eddy dissipation rate terms were obtained from direct measurements. The turbulent kinetic energy budgets were determined with respect to height and horizontal distance upwind and downwind of the mountain. The change of turbulence intensity was also demonstrated by comparing power spectra as a function of height, as well as a function of distance upwind and downwind of the mountain. The results show that all measurable terms were significant. The shear production and the eddy dissipation rate were the dominant terms. The buoyancy and vertical transport terms were smaller but still important. The imbalance term was estimated to be relatively small.

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