Artificial Rain! Really?

Various systems try to make it rain at will, although some experts remember its drawbacks and doubt its effectiveness

Scientists have been developing techniques for artificial rain for decades, so that this valuable resource can be counted on when needed, be it to combat drought, a fire, or even to clean a place.

The most widely used system today is to bombard the clouds with silver iodide, either from a small plane or from the ground with rockets or by means of generators that operate as a stove. In this way, the water crystallizes, forming snow or small hail, which melts as it descends into rain. Also, cloud seeding is used to remove fog and clouds at airports, in this case with carbon dioxide. For their part, some farmers use it to prevent hail from falling on their crops.

China is one of the countries that uses this system the most. According to Chinese authorities, a fire that destroyed 8,300 hectares of forest in the north of the country last year was extinguished thanks to artificial rain. A few months ago, storms had filled Beijing with sand from the Gobi desert. To clean it up, the city officials claimed to have resorted to “bombardment” of the clouds with silver iodide and other substances.

Also, the Chinese institutions affirm that they also use this system to avoid precipitations in a certain place. In this sense, the city council of Beijing has promised that it will bombard the clouds to ensure that it does not rain at the opening ceremony of the Olympic Games on August 8, 2008. The legend that it never rains in Moscow’s Red Square during the celebrations of May could be due to silver iodide.

However, some experts consider these statements a propaganda maneuver, stressing that these systems are subject to several limitations that do not allow such a degree of effectiveness and specificity: There must be clouds close to the place where water is desired; swamps in areas where clouds do not discharge; and that what is produced is rain and not hail. In this sense, the cloud bombardment could have been the source of the heavy hailstorms that fell on Beijing in the summer of 2005, causing serious material damage.

In addition to China, other countries trust in the development of this technology. Cuban scientists have resumed research to provoke artificial rains that help counteract a drought that has lasted more than a decade. The works began in 1978 with scientists from the Soviet Union, but were suspended in the early 1990s after the fall of the USSR. In Spain, the Community of Madrid announced last year the possibility of causing artificial rain following a method used in Israel.

< style="text-align:justify"p>However, scientists point out that cloud seeding has several drawbacks. First, they ensure that the excessive use of chemical products can cause damage to water, soil or living beings. In addition, the modification of the rain regime creates legal problems, since complaints could be received from neighboring areas for “theft” of its clouds. The issue has been raised at the United Nations and other international forums, and although there is no final decision, many countries have banned these practices.

Heat islands and artificial clouds

Another idea that seems to arouse a little more optimism among the scientific community is to create artificial clouds that then generate rain. Several researchers from Israel’s Ben Gurion University, the Free University of Brussels and NASA claim to be the first to accomplish this feat. The “Geshem” Project (rain in Hebrew) consists of covering surfaces of between 4 and 9 square kilometers with a black thermal material that absorbs sunlight. In this way, air will rise with 40 to 50 degrees Celsius higher than the prevailing temperature, generating clouds that would end up causing precipitation.

The system is based on the phenomenon known as “heat island” of cities, which can have up to 10 degrees more temperature due to asphalt and buildings. The idea had already been proposed in the 1960s, but the right material to achieve the temperature increase was lacking. The Israeli company Aktar, specialized in particular surfaces, has been in charge of developing it.

According to those responsible, the project is especially suitable for desert areas with a sea less than 150 kilometers away. Also, they add, its cost could reach 40 million euros, although it has no maintenance costs and is “ecological”.

It is currently in the experimentation phase in the Negev desert (Israel), and the results are expected to arrive in two or three years. For their part, Spanish scientists from the universities of Salamanca, Rey Juan Carlos of Madrid and Brussels are also collaborating on this project, thinking of moving it to the Mediterranean coast.

However, various experts in Atmospheric Sciences doubt its real possibilities, remembering that the mechanisms of rain are more complex than what this project proposes. In addition, they remember the environmental impact of the surface where the material would go, or the fact of generating rains where they do not usually occur naturally. In this sense, they recall, if precipitation occurs in a certain area, it will stop doing it elsewhere.

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