How often does it rain. So why is it raining? That is, the reason for everything is global weather changes.

Rain formation is directly related to one of the key natural mechanisms of our planet - the water cycle. On Earth there are many rivers, seas and oceans, the water in which tends to evaporate.


This happens under the influence of sunlight: the Sun heats the surface of the water, and the large drops that make it up turn into tiny ones that form light steam. It rises and enters the atmosphere. Depending on the air temperature, a certain amount of moisture is retained in the atmosphere.

Gradually, it condenses, and clouds form in the sky. Not all of them become rainwater, but sooner or later the accumulated water in vapor or droplet form again falls into water bodies and onto land, from where it either penetrates underground and then again enters water bodies in the form of groundwater, or again evaporates from the surface.

What happens inside the cloud?

Moisture in the clouds is able to travel great distances - it is supported by ascending air currents. Drops of water fall on the ground only after they become large and heavy enough. Inside the cloud, the process of vapor condensation continues: particles of vapor from the air settle on the smallest drops of water.

Droplets inside the cloud move in different directions, collide with each other and connect with each other. But clouds are not only accumulations of a large number of water drops, they are also a mass of tiny ice crystals. If there are only water drops in the cloud, their enlargement occurs very slowly - in one raindrop there are about a million of these tiny droplets of vapor.


And if the cloud is mixed, then water drops are in its lower part. And in the upper, in the area of ​​colder air, the same ice crystals are concentrated in the cloud. Rain in such a cloud forms quite quickly. And sometimes it happens that warm air rises very quickly in summer, and at high altitude, under the influence of negative temperatures, the drops massively turn into pieces of ice and fall to the ground in the form of hail, not having time to melt.

After it starts to rain, new currents of moist air replenish the rain cloud, and this continues until the flow of moisture weakens. In summer, each cubic kilometer of a rain cloud can contain about a thousand tons of water. The largest rain clouds, from which real downpours will spill, are formed on hot days, when a large amount of evaporating moisture rises from the surface of the earth into the air.

The cloud grows, increases in size and gradually its top reaches the cold layers of air. Approximately at an altitude of eight thousand meters above the ground, the air temperature can be up to minus thirty degrees. It is in this extreme cold that vapor drops crystallize into ice.

Often, when we see a dark cloud, we think that now. But the darkest gray clouds can pass by without shedding a drop of moisture. A sure sign that the cloud is really a thunderstorm is its blue-lead hue.

Where on earth does it rain more often?

The frequency and intensity of rains in different parts of the planet depends on the atmospheric pressure belts. At the equator, the air is constantly heated, there is an area of ​​​​low pressure, and the warm air, rising up, is regularly cooled.


That is why huge rain clouds constantly form in the equator region and heavy rains fall. This also happens in other parts of the planet, where the climate is determined by areas of low atmospheric pressure. The air temperature is also important: the higher it is, the more often it will rain in this place.

Where high-pressure belts dominate, descending air currents reign. Cool air, descending to the surface of the earth, heats up and becomes less saturated with moisture. In latitudes of 25-30 degrees, it rarely rains, and at the poles there is almost no precipitation.

Moisture Coefficient and Precipitation Observations

The level of humidity in a particular area is usually determined using the moisture coefficient. It is calculated by dividing the annual rainfall by the evapotranspiration over the same time. The lower the humidity coefficient, the drier the climate.

Provided that the annual precipitation is approximately equal to evaporation, the moisture coefficient is close to unity. This pattern is observed in forest-steppes and steppes. If the coefficient is greater than one, then the territory is characterized as an area with excessive moisture. If the coefficient does not exceed 0.3, the territory is characterized as an area with poor moisture - such areas include deserts.


Climate scientists measure the amount of precipitation in a particular part of the planet. Experts recorded an absolute minimum of precipitation - this is the situation in the Libyan Desert and the Atacama Desert, where less than 50 millimeters of precipitation falls per year.

The absolute maximum falls on the Pacific region (Hawaii) and Indian Cherrapunji, where more than 11 and a half thousand millimeters of rain falls every year.

Rain is one of the most common weather phenomena. However, not everyone knows why it is raining, although this information was given by teachers in elementary grades. The global water cycle begins with thermal effects. Under the scorching rays of the sun, liquid evaporates from the surfaces of reservoirs, rivers, seas and oceans. It turns into steam and rushes up. In countries with high humidity, small bubbles can be easily seen.

Reasons for the appearance

The sciences that study any kind of precipitation are called meteorology and climatology. They identify 4 main reasons:

1. Elevated landforms.
2. Ascending movement of air masses.
3. The presence of water vapor, which contributes to the formation of precipitation in the form of rain.
4. Meeting and interaction of flows of cold and warm air.

You can conduct a small experiment at home and see clearly how the world water cycle occurs.

To do this, you need to take a small container, draw water into it and put it on the fire to boil. Cover the pot with a transparent lid. When the liquid heats up, it will begin to turn into steam, and small droplets will begin to accumulate on the surface of the lid, and then fall back into the pot of boiling water and turn into steam again.

Upward movements

The sun's rays heat the earth, and the process of evaporation of moisture begins. This happens not only with soil, but also with water surfaces. The evaporated liquid is in the air. According to the laws of physics, warm air moves to the upper atmosphere along with the water bubbles it contains.

Basic physical concepts- absolute humidity (the amount of steam that is contained in the air at the current moment) and relative (in relation to the humidity that is observed at a given temperature). The hotter the air, the more water vapor it contains.

All air currents contain moisture, but the higher it rises, the lower the air temperature becomes. It starts to condense and clouds appear in the sky. When the temperature reaches the lower mark, and the cloud is no longer able to hold the amount of moisture that it contains, it starts to rain.

The process is similar to what happens with ascending air masses. The precipitation rule only works if there is a place for water bubbles to come from - from a leaf plate, water surface, freshly plowed soil, etc.

But if a person is, for example, in the Sahara desert, the sun's rays will not cause rain, since moisture has nowhere to come from.

Meanwhile, the evaporation of water from the surface of the soil and water bodies continues. The wind knocks together small flocks of fog. A cloud forms. Tiny droplets of water vapor move randomly, sometimes they merge and become larger during collisions. However, this is not enough to start.

For this to happen, the droplets must become large and heavy enough that the updrafts of air cannot hold them. One raindrop is obtained by merging with a million other cloud droplets. This is a very lengthy process.

Rain clouds form in the troposphere, the lowest layer of the atmosphere. The troposphere is heating up, so the air temperature near the surface of the planet is very different from the temperature a few kilometers above it - it drops by an average of 6 ° C for each rise. Even in the summer heat, at an altitude of 8-9 km above the Earth's surface, downright arctic cold reigns, and temperatures of -30 ° C are not uncommon here.

Processes inside the cloud

Water vapor, rising up along with air currents, gradually cools down, and then freezes, turning into tiny ice crystals. Thus, in the upper part of the rain cloud there are ice crystals, and in the lower part there are water droplets.

Water vapor condenses inside the cloud. As you know, this process is possible only in the presence of any surface. Water vapor settles on water droplets, all kinds of dust particles and motes raised up by ascending air currents, as well as on ice crystals. The size and weight of the crystals rapidly increases. They can no longer stay in the air and break down.

When passing through the thickness of the cloud, the ice crystals become even larger and more weighty as the condensation continues. If the temperature is above zero at the lower boundary of the cloud, the ice floes melt and fall to the ground in the form of rain; if it is below zero, hail occurs.

And then everything starts all over again. Numerous rain streams form that replenish terrestrial reservoirs. Some of the precipitated moisture seeps through the soil and enters underground water bodies. And part of the water evaporates, and a cloud forms above the earth.

Every person has experienced this natural phenomenon. We all hid from the rain under umbrellas many times and have long been accustomed to checking if there are clouds in the sky before a walk. And the most curious are sure to ask the question, where does this rain come from?

Where does the water for rain come from in the sky?

It turns out everything is very simple. Under the influence of solar heat, the smallest droplets of water evaporate from the surface of the Earth. These droplets are very small, almost invisible to the eye, such small droplets are called water vapor.

Water evaporates from the leaves of trees, from the surface of the earth and even from the surface of our body. Most of the water, of course, evaporates in the form of steam from the water surface of rivers, lakes, seas and oceans.

Evaporation over water can be seen in the early morning, when the vapor begins to collect in droplets right above the water. And you can also see such steam when the kettle boils.

Rising higher and higher, the vapor enters the cold layers of the atmosphere and collects in water droplets and tiny ice floes. After all, the temperature at the top, where the clouds gather, is about zero degrees. The wind collects droplets into huge bizarre clouds. You can see before the rain how white clouds gather into a cloud before our eyes darken. This is because there is so much water in the sky that it blocks out sunlight.

It happens that droplets freeze due to low temperatures and, together with raindrops, fall to the ground. It's hailing.

The droplets in the cloud connect with each other, become heavier and begin to fall to the ground. So it starts to rain.

Why does it rain more often in autumn?

Rains in Russia in autumn are even less frequent than in summer. According to weather forecasters, the largest amount of precipitation falls in June. And in autumn, due to the large number of cloudy days, it seems to us that autumn is rainy.

In winter, evaporating water vapor does not even have time to gather into droplets, but immediately turns from steam into fluffy snowflakes. Yes, snowflakes are formed from steam. And then instead of rain in winter it snows.

Now you know how water gets into the atmosphere and why it rains. Once on the ground in the form of rain or snow, water goes into groundwater, into the seas, oceans, rivers, lakes, and other bodies of water, and everything starts again and again. This natural phenomenon is called the water cycle.

Without such a water cycle, our planet would turn into a lifeless desert.

You can arrange a small water cycle even at home. For this transparent cover and put on fire. You will see how the steam will rise, settle on the lid, in the form of droplets. And the drops will fall down to rise up again, turning into steam. Such a wonderful rain in a saucepan.

Children are very fond of frolicking in the summer rain, walking in puddles, measuring their depth, and launching boats in murmuring streams. And in childhood, everyone, without exception, worries question – why is it raining?
When the sky is covered with gloomy, dark clouds, the drops in them become heavier and larger. Not staying in the air due to their own weight, the drops fall to the ground - it's raining.
Where and why is there water in the sky, in clouds and clouds?
There is a lot of water on earth - it is found everywhere: in lakes, rivers, seas, in the leaves of trees, even the human body consists of 80% water. Under the influence of solar heat, this moisture begins to evaporate from the surface of the earth. Very small droplets of water evaporate - so small that they are almost invisible - these droplets are called water vapor. Most of the water evaporates from large lakes and rivers.
How evaporation occurs can be seen in the early morning - smoky white steam begins to creep over the river, sometimes it is also called fog. Also, when a kettle or pot of water boils, the water evaporates, forming steam.

The answer to the question - why does it rain: the water cycle in nature

Evaporating, water droplets rise higher and higher into the sky, and the wind collects them into whimsical snow-white clouds. Over time, there are more and more water droplets in the cloud, and due to the large amount of water, the cloud stops transmitting sunlight. It is getting bigger, darker and heavier and is no longer called a cloud, but a cloud. And from this cloud, heavy drops of water, connecting with each other, fall to the ground in the form of rain.
Sometimes, when it is very cold upstairs, the droplets freeze and fall in small pieces of ice - this is called hail.
In winter, due to frost, the steam does not even gather into droplets, but immediately becomes snowflakes, which have the most varied shape. In winter, it does not rain - instead of water, such fluffy snowflakes fall on the ground.
Evaporating water falls into the clouds, from there again to the earth, in the form of rain, snow or hail, hitting the soil, the water goes into underground water, saturating rivers, lakes, seas. This cycle is called water cycle in nature.

At home, you can conduct such an experiment: put a saucepan with a transparent lid filled with water on the fire. Evaporating, water, in the form of steam, will rise to the top, remain droplets on the lid, and then fall down, subsequently evaporating again. So at home you can make your own rain, and observe the water cycle in nature.