Researches On Cloud Model With Spectral Bin Microphysics

Ice multiplication process is introduced into one-dimensional rain category model, and effect of ice multiplication on precipitation of stratiform cloud is explored numerically. Seeding effect of AgI and liquid CO₂, and the distribution and evolution of supercooled liquid water in the seeded stratiform cloud are studied. It is concluded that growth process of supercooled liquid water begins at 200 min, vapour content contributes a lot to the growth process; Better seeding effect can be achieved by liquid CO₂ seeding in rich supercooled liquid water region.A 3-D convective bin cloud model has been developed on the basis of the IAP 3-D hailstorm numerical model and the 2-D slab-symmetric model with spectral bin microphysics, and simulated a real cloud case. Results are compared with IAP 3-D hailstorm numerical models, It indicates that the maximum of updraft velocity obtained from bin cloud model depicts the two updrafts in observations well; and the strength, height, and width of radar echo simulated by bin cloud model is more close to the observations.Effect of the initial perturbation of relative humidity, potential temperature and CCN concentration on development of convective cloud has been explored respectively based on the 3-D convective bin cloud model. As the initial perturbation of relative humidity increasing, the maximum updraft appears earlier and higher, accompanied with the increase of the maximum liquid water content and drop concentration, as well as the widen of drop mass distribution function which can accelerate the formation and growth of graupel particles.There is a positive correlation between the initial perturbation of potential temperature and the maximum updraft velocity, liquid water content and drop concentration. With 2.5℃perturbation of the potential temperature, the maximum of updraft velocity, liquid water content and drop concentration increases to 41.7 m s^-1, 9.6 g kg^-1 and 626.2 cm^-3, respectively.The increase of the total CCN concentration induces the increase of the maximum updraft velocity, liquid water content, drop concentration and radar reflectivity. The decrease of the total CCN concentration accompanied with the reduction of the maximum drop concentration and the enhancment of the maximum liquid water content. The enhancement of CCN＞0.04μm and＜0.04μm both accompanied with the increase of the maximum drop concentration and liquid water content.The enhancement and reduction of the total CCN concentration both have negative effect on the formation of the graupel particles and large drops. With respect to the CCN＞0.04μm, the increase of CCN concentration＜0.04μm has more apparent effect on the diameter and mass distribution function of drops, especially the mass distribution function of drops melted from graupel particles.