Dry deposition

Removal of a gas or particle to a surface without precipitation. A simple parameterization uses downward flux $F=v_{d}C$, where $C$ is the concentration near the surface and $v_d$ the deposition velocity. For a well-mixed layer of depth $H$, the loss is first order with coefficient $v_d/H$.

The ratio of a specified downward dry deposition flux to its reference near-surface concentration. It has units of speed but need not be an actual particle settling speed: transfer resistance and surface uptake can both control gas dry deposition.