Cloud sowing: what is it, how it works and problems

Cloud planting is an artificial alternative whose main objective is associated with Change the amount or type of rainfall that occur in a certain region. In other words, it is a time manipulation by the human being that was discovered by Vincent Schaefer in July 1946 and that seeks to enhance a natural process of the atmosphere, increasing the number of condensation nuclei that exist in the clouds through air or terrestrial planting techniques. Cloud planting is not only used with the aim of increasing rainfall, but You can avoid the formation and fall of hail and even suppress the fog.

Cloud sowing consists mainly of placing a adequate proportion of condensation or crystallization nucleibeing the most used silver iodide (highly insoluble in water with a structure similar to ice), dry ice or carbonic snow and even salt (hygroscopic particle). In order for this process to occur, it is necessary that the clouds be susceptible to planting, being very cold ideals with temperatures that range between -10 ° and -20 ° C, and with significant amounts of over -up water. The cumulonimbus (Vertical development clouds) They are usually chosen for this process. It should be noted that through this mechanism you cannot form clouds where they do not exist and that although many times it is thought that silver iodide is used so that it does not rain, it is actually to avoid another more dangerous precipitation type: hail.

Below we present different steps to explain how aerial and terrestrial clouds work.

Aerial cloud planting

1. First, the plane (medium used for cloud planting) crosses a cloud that meets the necessary conditions to be sown. Airplanes have flags and other ejectable devices that They release silver iodide in the clouds.
2. Iodide particles act as condensation nuclei and They attract water droplets.
3. The droplets that are at more than 0 ° C adhere to the compound subsequently forming Ice crystals.
4. The ice crystal falls by its own weight.
5. When passing the freezing level, The drops become liquid And they begin rainfall.
6. When the water drops fall, they generate hot air currents that rise, causing a greater amount of rain.

Sowing of terrestrial clouds

1. In the first instance, silver iodide with liquid acetone is burned. The resulting product is smoke to the cloud which meets the necessary conditions to produce planting.
2. Then, ascending air currents allow silver iodide to rise and reach the clouds.
3. Inside the cloud, there are drops of water that fail to bind by themselves to produce rain, so the silver iodide acts as an binder particle and Small drops of water bind to it.
4. Finally, water drops increase in size and fall by its own weight in the form of rain.

We recommend reading this article about the cumulonimbus clouds: what they are and how they form.

In general, cloud fertilization uses mainly small concentrations of silver iodide that can generate a negative impact on people and the environment. However, there are studies that have shown that In the short term there is no riskgiven that:

• Small amounts are used in the sown.
• It is insoluble, little mobile and low bioavailability.
• The small proportion that can be toxic that dissociates, tends to adsorb and in the event that it reaches certain organisms, the retention rates do not exceed 10%.

It is important to highlight that cloud planting is a controversial technique and that there are still many doubts on its long -term effects and it is important that more research be carried out to better understand the potential impacts of cloud planting before it is implemented on a large scale.

They currently exist More than 37 countries around the world in which clouds are sown with different objectives. The China People’s Republic It has one of the most impressive systems, increasing the amount of rain in numerous arid regions, including its capital, Beijing. In addition, USA It uses the planting of clouds with the purpose of increasing rainfall in areas with high drought, to reduce the size of hail and the amount of fog present at airports. In fact, this methodology is also used to increase snowfall in important ski centers. In Southeast Asia this process has been used to improve air quality. Another country that also uses the method of planting clouds or artificial rain is Dubai.

On the other hand, the planting of clouds in Spain has a long history. Between 1979 and 1981, the project for the intensification of precipitation (PIP) was carried out, coordinated by the World Meteorological Organization (OMM) whose objective was to study the viability of the planting of clouds to increase rainfall, avoiding economic losses in agriculture by drought. However, despite the experiments of the past, cloud sowing is not currently used regularly, since there is no scientific consensus about its effectiveness. Other countries like Argentina, Chile, Venezuela and Mexico They also use this artificial modification mechanism.

Now that you know what clouds are sowing and how artificial rain is done, you may be interested in this article about hydrometeoros: what are and types.

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