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SECOND STEP LIANG-HAI-OAN (FATTEN): To activate or stimulate cloud evolution by dispersing endothermic and hygroscopic chemicals several thousand feet above cloud-base level either directly in, around, or imme- ~ diately upwind of existing cloud. CHOME-TEE (ATTACK) THIRD STEP To stimulate and enhance the rainfall in a variety of ways including; dispersing dry-ice or a combination of endothermic chemicals into clouds near the 10,000 ft level, hygroscopic and endothermic chemicals immediately below cloud base to enhance precipitation development and/or lower cloud bases. While being conceptually plausible, the specific technical aspects of this approach have not benefitted from scientific evaluation using either modeling techniques or comprehensive physical and statistical analyses. E. Program Implementation The principal function of the RRRDI is to provide operational cloud seeding to those provinces and districts that request such :service. Table 111-3 presents an overview of the seeding activities with'in the year; table 111-4 presents a sunrnary of annual requests; and table 1II-5 provides an accounting of the activities over the years (1971-1985). Cloud seeding operations for precipitation enhancement purposes al~e systematically con- ducted from March through October moving through thl! various regions and provinces. 1. Annual operational program In some years (e.g., 1979) the number of provinces requesting cloud seeding were as high as 63 of the 71 provinces of Thailand. In 1985 there were 41 provinces requesting seeding operations. The RRRDI program makes use of numerous aircraft and substantial quantities of seeding materials in their operations; a summary of which is provided in tables 111-6 and 111-7, respectively. The annual operational program can be generally described as follows: March-Aprir - During this period of southeast fl()w cloud seeding acti- vities are conducted by three rainmaking teams in the eastern and southern parts of Thailand. Regular cloud seeding activities are imple- mented for orchards, pararubber, coconut, pineapple, and tapioca plan- tations, etc. Occasional activities are conductl!d for water consumption in remote and non-irrigated areas and for the re'lief of water pollution in rivers. ~ May-October - During the southwest monsoon period cloud seeding acti- vities are conducted by three to five rainmaking teams in the northern, northeastern, 'and central parts of Thailand. Regular seeding activities are implemented for paddy and field crops under cultivation. Occasional f . 26