Stokes number, \(St\)

https://doi.org/10.1351/goldbook.S06029
Sometimes referred to as the inertial parameter; it is an index of the impactability of an @A00176@ particle. It is defined by the equation: \(St = 2\ \tau \ (V_{\text{t}}- v_{\text{t}})\ D_{\text{p}}\) where \(D_{\text{p}}\) is the diameter of a small drop, \(V_{\text{t}}- v_{\text{t}}\) is the difference in fall velocities of the drop and @A00176@ particles and \(\tau \) is the characteristic @R05287@ of a particle.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2216 [Terms] [Paper]