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Chapter 11 Momentum and Heat Exchanges with Homogeneous Surfaces

Elsevier Science & Technology
DOI: 10.1016/s0074-6142(08)60426-x
  • Earth Science


Publisher Summary This chapter describes momentum and heat exchanges with homogeneous surfaces. The Monin–Obukhov similarity theory provides the most suitable and acceptable framework for organizing and presenting the micrometeorological data as well as for extrapolating and predicting certain micrometeorological information where direct measurements of the same are not available. The basic similarity hypothesis first proposed by Monin and Obukhov (1954) is that in a horizontally homogeneous surface layer the mean flow and turbulent characteristics depend only on the four independent variables—namely, the height above the surface z, the friction velocity u, the surface kinematic heat flux H0/ρcp , and the buoyancy variable g/T0. The best micrometeorological experiment conducted for the specific purpose of determining the M–O similarity functions, is the Kansas Field Program. A 32-m tower located in the center of l mile field of wheat stubble is instrumented with fast-response cup anemometers, thermistors, resistance thermometers, and three-dimensional sonic anemometers at various levels. These are used to determine mean velocity and temperature gradients as well as the momentum and heat fluxes using the eddy correlation method. Some of the other methods of determining momentum and heat fluxes include surface-drag measurements, energy balance method, and bulk transfer method.

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