Physical Foundations of Clouds

The current technology related to the physical processes of rainfall formation has allowed to modify the traditional belief that the atmospheric variables are unmanageable. This development has put in the hand of man the possibility of increasing the water resource, intervening in the hydrological cycle in the phase of precipitation. How is this phenomenon possible?

1. The formation of artificial rain with Silver Iodide

To understand how rainfall can be manipulated, we must first know what the clouds are made of. These are made up of microscopic droplets of water and ice crystals. For the formation of a raindrop, it is necessary that thousands of these droplets come together to acquire sufficient weight and fall to earth by gravity. On the other hand, cloudiness also contains particles of supercooled water, ie water droplets that remain in liquid state despite being at temperatures several degrees below zero.

In order to produce artificial precipitation, the hydrological cycle and the formation mechanics of the same are involved, increasing the number of “freezing nuclei” inside the cloud cover. In this process, the best practical result has been the Silver Iodide, whose molecular conformation is similar to that of water, providing extra freezing nuclei, which is injected or introduced into the cloud. Such injection of freezing nuclei causes water particles to be “supercooled”, ie particles which remain in the liquid state despite being at temperatures below 0 ° C (and even in the gaseous state) to adopt the state capable of falling, that is, the solid state (ice). Figure 1 illustrates what is expressed.

Figure 1: The left image points to the water molecule (H2O) in a normal cloud, the center image shows the water molecule (H2O) that has been injected with Silver Iodide (AgI) and the image The right imager illustrates the transformation of the water molecule (H2O) thanks to the action of Silver Iodide (AgI), transforming into a solid element.

This change of state (liquid to solid or from gas to solid) produces a release of latent heat to the atmosphere, generating a heating in its surroundings, in other words, the cloud, increasing its instability. This causes the ascending and descending currents of air within them to intensify, making it grow both vertically and horizontally. This leads to a general intensification of the stormy activity in the cloudiness and, in the end, increases precipitation fall.

Another effect of the introduction of Silver Iodide in cloudiness is that it can serve as the condensation core in the coalescence process, ie in the process of agglutination of the water particles until reaching enough weight to fall to earth. In other words, this compound acts as a solid particle, in which the water droplets adhere to form a drop of rain.

It should be noted that this type of solid particles are present in natural shape in the atmosphere, in the form of salts, smoke, dust, etc., but Silver Iodide behaves as a nucleus of ideal characteristics to fulfill this process. Figure 2 illustrates this idea:

Figure 2: The image on the left illustrates the H2O molecules of a cloud; in the center image we see the Silver Iodide (AgI) in the cloudiness that acts as condensation nucleus in the process of coalescence, hence, it agglutinates the microscopic droplets of water; in the right image we appreciate how H2O and Silver Iodide have united and reach enough weight to fall to earth.

2. Silver Iodide (AgI): characteristics and environmental conditions for its application

To introduce Silver Iodide (AgI) in a cloud requires certain climatic conditions. Usually, bad weather events are useful because they are associated with an extensive Low Pressure area. Low pressures are characterized by intense upward air currents. This characteristic is used by the technique of planting of clouds by terrestrial generators, since these currents are those that are in charge of transporting the nucleant (AgI) from the terrestrial surface to the interior of the cloudiness in few minutes, reaching the propitious levels of temperature to develop the maximum potential of the system.

Each gram of Silver Iodide (AgI) adds 10 to 13 additional condensation or freezing nuclei to the atmosphere. With this important amount of nuclei artificially introduced in the cloudiness, an average precipitation increase of the order of 15% is obtained, depending on many factors, such as the opportunity of sowing, the degree of activity of the cloud systems, the intensity of upstream currents, the amount of supercooled water present in the cloud cover, etc.

• Publicado por: Mettech
• April 26, 2018