SEPTEMBER 24, 1955
NEW YORK—Since I have started to tell you something about UNESCO's various projects I think there is another one that will be really interesting to you.
There are places in our own country where we have experimented with "seeding the clouds," as we call it, to make rain, and some of us have followed these experiments with some interest. But rain is so important in the deserts of Baluchistan and Sindh, where normally only five inches of rain fall in the whole year, that a project to get more rain there is of vital concern to everyone. In the Punjab a rainy day is one of the big events of the year.
So, with the hope of getting more rain the government of Pakistan appealed to UNESCO three years ago for a scientific mission to help them decide whether it was economically feasible to undertake "cloud seeding" in some of these areas. Since then some Pakistani meteorologists and a young scientist from UNESCO have found—and have had some successful tests in the Punjab—a new low-cost process for increasing rainfall by literally salting the sky.
Two test regions covering about 1,500 square miles, where the experiments were held in July, August and September of last year, showed on the rain gauges in the area that 50 percent more rain had fallen in these areas than in adjoining regions.
The way it was done was through the use of small hand blowers such as the silversmiths of Pakistan use in bazaars. Being manufactured locally the cost is less than $30, and with these small blowers they wafted eight tons of salt into the sky during the experiment.
Most of our "cloud seeding" aims at producing ice in the upper parts of the clouds, but that is impractical in warm countries where rain often falls from clouds which come nowhere near the freezing level. The Pakistani meteorologists working with the UNESCO team suspected that rain in warm countries may be formed on the tiny salt particles that come from the evaporation of sea spray but nobody knew how far inland these particles penetrated.
Patiently they worked for two years in various parts of Pakistan among other things taking samples of the dust in the air to determine salt content. Near the shore they found that there were always thousands of salt particles in each cubic meter of air. Further inland in the Punjab there was less than 10 percent a cubic meter.
It would take too long to describe the mechanism that they developed but it was simple and inexpensive, and the UNESCO scientists as well as the Pakistani people feel the method has great promise for tropical countries that cannot afford the expensive large-scale "cloud seeding" experiments with aircraft.
The salting in the Punjab for 39 days cost only $1,000. The records showed daily reports from 200 rain gauges dating as far back as 1900, and it was learned that the 1954 rainfall pattern had not been equaled since 1914.
The new Geophysical Observatory at Quetta is now considered one of the best in Asia. The work of these Pakistani meteorologists in conjunction with the UNESCO team has already been published in international scientific journals and it is gaining for Pakistan an honored place in the science of geophysics.