Or at least it seems so to me. By creating very high surface temperatures with black plastic, the idea is to promote convective instability through the release of latent heat of vaporization of water, and generate an artificial cloud, and, with luck, a thunderstorm. Trouble is, I don't think they realize just how readily the hot air will mix with surrounding air, therefore lowering its temperature, and just how large an area they'd have to cover with the plastic:
They will spread large sheets of black solar-absorbing film over perhaps 9 square miles of land to generate intense heat. How long the plastic sheeting will withstand the natural elements is not clear from the article.
Energy from sunlight, absorbed by the material, will radiate upward, heating the lower atmosphere.
Scientists hope the heated air will lift water condensation high enough to form clouds and produce rain.
"I'm always interested in looking at anything that will make it rain," Grant told me by phone from his office in Big Spring. He added that the Negev project is all new to him.
The area between San Angelo and Del Rio is about 30 degrees north of the equator - virtually the same latitude as Israel's Negev Desert. A major difference, however, is that West Texas has no major bodies of water within 100 miles - unlike the Negev's nearby Mediterranean Sea.
"I guess the proof will be whether they can put it in and see what happens," Grant said. He oversees cloud-seeding across a 1,000-square-mile area of Borden, Scurry, Mitchell and eastern Howard counties, north and northwest of San Angelo.
...Over areas such as West Texas and the Negev Desert, normal air currents prevent water vapor from rising high enough to form clouds.
Israel's rainmakers say installing large black patches could raise the surface temperatures by 120 degrees, and thus create a chimney of fast-rising air currents. The artificial thermal would then lift the water vapor to about 10,000 feet elevation, where it can condense into water droplets that create clouds.
Clouds up to 20 miles long would form from noon to 5 p.m. daily above the black plastic, then drift with winds and shower nearby lands.
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