Rain, synonymous with life and joy for many, and a miracle for others—perhaps because in their places it's rare to see a drop of water fall from the sky— is a crucial factor in the life cycles of planet Earth. Rain itself speaks to the water cycle in our atmosphere.
For rain to occur, it's essential to start with its source: water, one of the most important biomolecules on our planet, making up 70 percent of our Earth's composition. And, surprisingly, 75 percent of our bodies are composed of it.
It is therefore not surprising that understanding the phenomenon of rain is essential for human beings , since it is the natural journey that water takes, even in the different states of matter that we know.
Water is made up of 2 hydrogen atoms (H) and 1 oxygen atom (O) linked by two covalent bonds, so that the molecule has a flat triangular shape, graphed in this way H20. That is, the hydrogen and oxygen atoms are separated from each other by approximately 0,96 Angstroms (more or less one nanometer – one billionth of a meter) and the angle formed by their bond lines is about 104,45 degrees.
Rain is an essential meteorological process for life
What is the process of the phenomenon of rain
According to the official definition of the World Meteorological Organization, rain is the precipitation of liquid water particles with a diameter greater than approximately 0,5 mm, or smaller but widely dispersed droplets. If this precipitation does not reach the Earth's surface, it is not rain but virga, and if the diameter is smaller, it is therefore drizzle. Rainfall is measured primarily in cubic millimeters, and various instruments exist for this purpose.
The phenomenon of rain depends essentially on three factors: atmospheric pressure, temperature and, especially, atmospheric humidity.
Water evaporated by the sun from lakes, rivers, and seas can return to Earth as snow or hail . Depending on the surface it hits, the sound it produces will be different, as we discussed earlier regarding the states of matter.
Rain is one of the most common and yet most surprising environmental phenomena, despite its simplicity. The ascent of water vapor is one of the main steps in the formation of rain. Clouds are made up of countless tiny water droplets , so small that there are an average of 500 in a cubic centimeter.
After water vapor forms clouds, the condensation process occurs, which is a thermal shock that causes the water to change from its gaseous state to a liquid state, promoting the union of its molecules, so that precipitation is subsequently generated.
The water taken from the earth through evaporation is thus returned to the liquid state in seas , rivers, and lakes: in this way the so-called water cycle is completed.
The so-called water cycle
From all of the above, it is logical to say that there are clouds in which the droplets remain small , and therefore remain suspended in the sky, while in a few other clouds the droplets grow larger, transforming into downpours, which, combined with other atmospheric conditions, are called storms.
Learn more about this topic here: WHAT IS THE GRAVITY OF THE PLANETS THAT MAKE UP OUR SOLAR SYSTEM?
Elements necessary to carry out the phenomenon of rain
Atmospheric pressure
Atmospheric pressure is understood as the force per unit area exerted by the air on the Earth's surface. The atmospheric pressure at a point is numerically equal to the weight of a unit straight, static column of air extending from that point to the upper limit of the atmosphere, to give an example.
Temperature
Ambient temperature represents the range in which the air feels neither too cold nor too hot when wearing casual clothing. This range is between 150.000°C and 300.000°C and is the temperature range used by climate control devices. Variations within this range cause water to evaporate from the Earth's surface.
atmospheric humidity
As we mentioned earlier, air contains varying amounts of water in the form of vapor; this is known as atmospheric humidity. Air humidity is the concentration of water vapor in the air—in other words, the amount, or number, of water vapor molecules per unit volume of air.
This unit can range from 0 to 4% of the volume. This wide variation is due to the fact that water can exist in all three states of matter—solid, liquid, and gas—at the planet's typical temperatures, as it interacts with the Earth's internal energies.
Learn more about this topic here: WHAT IS THE FIRST PLANET FORMED IN OUR UNIVERSE?
Places in the world where the phenomenon of rain is not common
Places where it hardly ever rains
Most of us live in a climate where rain, to a greater or lesser degree, is present. However, there are places in the world where it never rains, the earth trembles, and people have learned new ways of surviving, not in relation to water.
Wādī Ḥalfā in Sudan
In northern Sudan, on the shores of Lake Nubia , this small village receives a mere 2.45 millimeters of rain per year, making it the sunniest place on Earth with 4,300 hours of sunshine annually. Summers here are typically long and sweltering, with temperatures exceeding 40°C. To learn more about conditions in arid regions, we invite you to read the article on acid rain and its environmental impact.
Ica in Peru
The city of Ica is one of the most famous destinations in Latin America, located in southern Peru, thanks to its border with the Chilean Atacama Desert and attractions like the Huacachina oasis and the beaches of Paracas. It boasts a unique ecosystem shaped by the 2.29 millimeters of rainfall it receives annually and a summer that lasts from December to March. Interestingly, thousands of years ago, this was a place where penguin colonies thrived under less extreme conditions. For more information on the influence of climate in desert regions, you can consult the article on rainfall patterns.
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Luxor in Egypt
The city of Luxor, the glorious city located in southern Egypt, receives a recorded annual rainfall of only 0.862 milliliters. And this is only when it rains due to strong weather patterns from other regions, as Luxor is one of the driest places in the world, sometimes going for up to six years without any rain. The temperature in this city exceeds 40°C during the summer months, and Luxor is curiously one of the places with the greatest temperature difference between day and night, with contrasts of up to 16°C. If you are interested in learning more about places with extreme climates, see the article on rainwater and its storage.
Kufra in Libya
With only 0.860 milliliters of water per year, Kufra is considered the driest spot in Africa . A desolate landscape, it's famous for its agricultural project sustained by water from an underground aquifer. The only way to survive here is through small plots of land that form tiny green dots, also famous for being visible from space.
