CALCULATIONS PERTAINING TO HYGROSCOPIC SEEDING WITH FLARES

Some possible effects of hygroscopic seeding with flares are explored by calculating how such seeding would modify the initial size distribu tion of cloud droplets and the subsequent evolution of that size distr ibution by coalescence. To be representative of recent experiments in South Africa, the calculations emphasize the effects of hygroscopic pa rticles that can be produced by hares, instead of the larger particles used in most past hygroscopic-seeding experiments. Parcel calculation s representing simultaneous condensation and coalescence suggest that the formation of rain through the warm-rain process can be accelerated significantly by the addition of such hygroscopic particles. Some obs ervations of the effects of hygroscopic material near cloud base suppo rt at least the early stages of the calculations. The results suggest that the positive effects being obtained in the South African experime nt may occur through such acceleration of the warm-rain process. Possi ble cloud-seeding applications and climate implications are discussed.