The process is called cloud seeding, a technology that dispenses chemicals – usually ordinary table salt or sodium chloride instead of the more expensive silver chloride – in the clouds to hasten the coalescence or collision of cloud particles.
The Department of Agriculture-Bureau of Soils and Water Management (DA-BSWM) explains that as the combined particles increase in size and become heavy, they turn into water droplets and fall as rain.
Cloud seeding aircraft are usually Philippine Air Force planes equipped with special chemical dispensing facilities.
Over the past few weeks, cloud seeding has been conducted in selected areas of the country, including Western Visayas.
Cumulus or cumulonimbus clouds are the appropriate clouds for seeding purposes, according to the DA-BSWM. They are usually located at an altitude of at most 11,000 feet.
Cumulus is a massy cloud form with a flat base and rounded outlines often piled up like a mountain. Cumulonimbus clouds are shaped like an anvil.
Cloud seeding, according to the DA, offsets the effects of an extended dry spell by inducing rain in agricultural areas and critical watersheds that serve as the source of water for multipurpose dams.
For instance, during the El Niño episode in 1998, the country would have suffered much more had a massive cloud seeding program not been undertaken.
"The timely intervention of cloud seeding in major agricultural areas and watersheds in the country significantly minimized the devastating effects of the El Niño phenomenon on the agriculture sector of the country," the DA-BSWM reported.
Likewise, the decrease in the water level of Angat Dam in Bulacan that provided the domestic water requirement of Metro Manila was checked from slowing down.