Japanese weather modification activities have been surveyed. The principal works have evolved in three stages. During the early program from 1947 to 1960, the research was carried out in the major universities with sponsorship derived from the electric power companies. Many technical developments concerning the generation, detection, and behavior of artificial ice nuclei took place during this period. Experimental work was concentrated on ground seeding programs. Around the end of this period, the lack of basic knowledge in cloud seeding was realized while the practical program, although curtailed in some areas, continued operation. Tokyo Metropolitan Office of City Water Supply started developing a comprehensive but routine seeding program in order to secure the water supply in dry seasons.

The second period occurred between 1961 and 1967 when the Science and Technology Agency funded a five year project to the Japanese Artificial Rainfall Research Corporation for the purpose of obtaining more basic information on clouds and cloud seeding. This research was carried out in Kwanto and Kyushu Branches of the corporation.

In the third and most recent period starting in 1968, the research trend has been toward microphysics and dynamics of clouds with continuing effort on instrumentation development. Weather modification research of the hazard prevention type is currently emphasized.

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1 This study was supported by the Bureau of Reclamation under Contract No. 14-06-D-6444.