A Method of Estimating Vertical Eddy Transport in the Planetary Boundary Layer Using Characteristics of the Vertical Velocity Spectrum

Abstract

The vertical eddy diffusivity coefficient K is hypothesized to depend upon the parameters that determine the energy spectrum of the vertical velocity fluctuations. Vertical velocity spectra from the lowest 320 m of the atmosphere are used to verify a relation among the rate of dissipation of eddy energy per unit mass, the standard deviation of the vertical velocity fluctuations, and the wavenumber of the peak of the energy spectrum of the vertical velocity fluctuations. Observations at Round Hill, Mass., and Cedar Hill, Tex., are employed to verify that the vertical eddy viscosity KM is proportional to the product of any two of the above parameters. However, the Richardson number must be included with these parameters in order to estimate the vertical eddy conductivity KH. In addition, it is shown that the wavenumber maximum of the vertical velocity spectrum and the nondimensional ratio σw/u* may be approximated at heights less than 320 m by empirical formulae.