Extended resistance analogy for construction of the vertical diffusion scheme for dispersion models

A new physical analogy for the discrete approximation of the vertical diffusion equation is presented. It is based on the resistor‐capacitor chain and incorporates the classical resistance approach to dry deposition simulation in a natural way. It is shown that in the simplest case the finite chain of resistors and capacitors is equivalent to a second‐order discrete representation of the diffusion equation resulting from the K theory closure. However, the scheme provides several features, which either cannot be obtained from straightforward discretization at all, or would require a sophisticated construction for their justification and realization. The examples discussed include a thick model layer with a highly variable vertical diffusion coefficient and an internal emission source, interaction with a chemical transformation unit, and spectral features of the model's vertical structure.