# Structure function

From Glossary of Meteorology

## structure function

The variance of the difference of a turbulence quantity in space or time, given by where

*q*is a scalar or a velocity component.For small separations ( where is called the structure constant of

*r*≤*z*, where*z*is the height above the surface), this equation may be written*b*is about 0.7 for temperature and 0.76 for humidity, χ_{q}is the rate of destruction of*q*^{2}/2 by molecular diffusion, and ε is the rate of dissipation of turbulence energy into heat. The coefficient*q*. This formulation eliminates the mean component of a fluctuating quantity and provides a measure of fluctuation variance within a band of wavelengths (or frequencies) determined by the separation distance (or lag time).Panofsky, H. A., and J. A. Dutton 1984. Atmospheric Turbulence. Wiley, . 182–183.

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