Because the microscopic processes responsible for atmospheric mixing are too complex to model in detail, atmospheric modelers generally treat atmospheric mixing as a macroscopic "eddy" diffusion process. In this approach, the diffusion rate at each pressure level is parameterized by a quantity known as the eddy diffusion coefficient K (Chamberlain and Hunten 1987, pp. 75 and 90).
References
Chamberlain, J. W. and Hunten, D. M. Theory of Planetary Atmospheres: An Introduction to Their Physics and Chemistry New York: Academic Press, 1987.
