CALPUFF is a multi-layer, multi-species, non steady-state Lagrangian puff dispersion
model. Dispersion is simulated for discrete “puffs” of species emitted from modeled
sources. The puffs are tracked until they have left the modeling domain while calculating
dispersion, transformation and removal along the way. Since this process can take hours under low wind conditions, an important effect of non steady-state dispersion is that the
puff can change direction with changing winds, allowing a curved trajectory. The ability
to track this change would appear to give CALPUFF an advantage