In 1962, Doubleday published a book by Louis J. Battan titled "Cloud Physics and Cloud Seeding". In 2003, Dover republished it unabridged, but changed the title to "Cloud Physics: a popular introduction to applied meteorology". I bought the Dover edition about ten years ago, and was surprised to find that the title, which had attracted me, did not accurately describe the contents. The book languished on a shelf, until I recently went searching for anything I had that might help explain weather. It is still not a balanced introduction to meteorology, but it definitely is relevant to rainmaking. In fact, most people think that cloud seeding is the only way to make rain. There was some excitement a few years ago about electrical means for rain making, but I haven’t seen much about that lately.
I have some doubts about cloud seeding under drought conditions. A few years ago, I read a National Geographic article which described unsuccessful cloud seeding in northern China during a severe drought. It occurred to me then that you can generate silver iodide crystals and disperse them from ground level or aircraft to create nucleation sites for condensation in the upper atmosphere, or you can fire rockets to disperse nucleation sites at high altitude, but if there is insufficient moisture in the upper air, the droplets will evaporate before they can reach the ground. They may not even fall.
Dry ice pellets have been spread from aircraft flying above clouds. The clouds were modified, but no rain fell. As I write this I wonder why there has to be a cloud to do the seeding. Why can’t clear air be seeded with cloud condensation nuclei that will cause condensation? I suppose that the answer is that there are already aerosol particles up there and the absence of clouds indicates that the humidity and temperature are not right for condensation. Hence, seeding will not cause condensation. Where there are already clouds, seeding is an attempt to provide large particles that will collect small droplets that will cause the combined masses to grow and fall.
An Internet search reveals that there is some cloud seeding activity in the western mountain states to increase snowfall in the mountains, and some attempts to overcome drought in Texas. The companies that do the seeding claim some success. Author Louis J. Battan explains some of the statistical tests and experimental protocols required to prove that seeding actually works.
There is presently some controversy over test procedures in a cloud seeding program whose purpose is to prevent flooding, rather than overcome drought. In that program, salt crystals are being dumped on clouds offshore of Jakarta, Indonesia in an attempt to cause rainfall in the ocean, rather than on Jakarta. Salt is hygroscopic and should collect water droplets into drops large enough to fall in the ocean. An Al Jazeera video shows crew members cutting open large bags of salt crystals and dumping them into a funnel that feeds a pipe that passes through the bottom of the aircraft. They seem more intent on averting a flood disaster, rather than perfecting an experiment.
And so we go from one disaster to another, from drought to flood to insufficient winter snow pack. Work on cloud seeding has been going on for about 67 years. Results are unclear. Reminds me of Ocean Thermal Energy Conversion (OTEC). Success has been just around the corner for 100 years. Still no working OTEC.
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