V. Artificial Rain

2. The practice of artificial rain

The basic idea of artificial rain theory is that by spreading cloud seeds into the clouds it will increase the probability and the amount of precipitation. Therefore, first a suitable weather condition should be chosen; then, the artificial ice-crystal nuclei will be spread into the cloud to enhance the effectiveness of crystallization and thereby facilitate rainfall. In general it can be divided into ground rainmaking and aerial rainmaking.

a. Ground rainmaking

By using the ground rainmaker (Fig. 1) to burn a silver iodide solution, the particles float up to the sky with the smoke where they will act as ice-crystal nuclei. When the smoke particles of the silver iodide reach the supercooled water drop layer of the clouds, they will cause supercooled water to solidify into ice-crystals, and the ice crystal through a growing process will finally become rain.

The ground rainmaker

Fig. 1: The ground rainmaker.

b. Aerial rainmaking

An airplane is used (Fig. 2) to spread silver iodide or dry ice cloud seeds. Because the cloud seeds spreaded can be delivered precisely to clouds with cold enough temperatures, this method is in general more effective than ground rainmaking.









Fig. 2: CENNSA 421, the rainmaking airplane with a silver iodide burner under its wing.