A three-dimensional model of transport and diffusion of seeding agents within stratus

It is essential to learn the temporal and spatial concentration distributio ns and variations of seeding agents in cloud seeding of precipitation enhan cement. A three-dimensional puff trajectory model incorporating a mesoscale nonhydrostatic model has been formulated, and is applied to simulating the transporting and diffusive characteristics of multiple line sources of see ding agents within super-cooled stratus. Several important factors are take n into consideration that affect the diffusion of seeding materials such as effects of topography and vertical wind shear, temporal and spatial variat ion of seeding parameters and wet deposition. The particles of seeding agen ts are assumed to be almost inert, they have no interaction with the partic les of the cloud or precipitation except that they are washed out by precip itation. The model validity is demonstrated by the analyses and comparisons of model results, and checked by the sensitivity experiments of diffusive coefficients and atmospheric stratification. The advantage of this model in cludes not only its exact reflection of heterogeneity and unsteadiness of b ackground fields, but also its good simulation of transport and diffusion o f multiple line sources. The horizontal diffusion rate and the horizontal transport distance have be en proposed that they usually were difficult to obtain in other models. In this simulation the horizontal diffusion rate is 0.82 m s(-1) for average o f one hour, and the horizontal average transport distance reaches 65 km aft er 1 4 which are closely related to the background Fields.