Artificial rain

A technique to produce unnatural rain is being worked out in Mexico by researchers at the National Center for Atmospheric Research in Boulder, Colorado, USA and several universities in Mexico. They are using pyrotechnic flares mounted on aircraft to seed clouds. The craft flies along the surface of cloud so that the moisture-retaining particles released by the flares could rise into the cloud. When the water vapours in cloud come into connection with the particles, these are formed into droplets that fall as rain ( Popular Science , Vol 251, No 2).