Numerical Simulations Of Seeding Convective Clouds With Hygroscopic Particles

A 2D slab-symmetric nonhydrostatic cloud bin model was used to simulate the evolution of convective clouds and precipitation under different CCN conditions in the origin area of Three Rivers in Qinghai-Xizang Plateau and Yangtze-Huaihe River Valley. Meanwhile, the effects of various hygroscopic seeding on the precipitations were also investigated.The dynamical-microphysical processes and precipitation were analyzed. The results show that,1) the Three Rivers in Qinghai-Xizang Plateau cloud is mainly dominated by the cold-cloud process, the contribution of the ice precipitation is more than liquid precipitation, the Yangtze-Huaihe River Valley cloud is mainly dominated by the warm-cloud process, the contribution of the liquid precipitation is more than ice precipitation; 2) under the same initial thermodynamic and dynamic conditions, the low initial CCN concentration clouds produce raindrops, ice crystals, and graupel particles more effectively in both development and mature stages, resulting in a stronger radar reflectivity. With the increasing in CCN number concentration, excessive CCN particles limit the growth of cloud droplet and the formation of precipitation particles, moreover, the restraint of the growth of graupel particles was happened in cold process, the initial time of precipitation delayed, and the total amount decreased; 3) it is the nonlinear response of the initial CCN concentration to rainfall amount. When CCN from 100cm-3 to 500cm-3, the precipitation increases, then CCN concentration is higher, the rainfall amount is smaller.By the hygroscopic numerical simulated, it is found that 1) the rainfall enhancement can be achieve when seeding was conducted a few minutes after the cloud initiation and above the base of cloud. It was found that the most effective particles were those with radii larger than 1μm; the particle smaller than 1μum had a negative effect on the rain development.2) Under the same initial CCN concentration, the effect of seeding on detail precipitation was different in various thermodynamic conditions.