Rain: Formation of Clouds & Water Cycle

Rain, as we all have experienced in our day-to-day life, is droplets of water that are condensed due to evaporation. During the water cycle, the formation of clouds takes place. 

• Rain is also called precipitation. 
• It happens when many droplets of water combine to form larger and heavier drops.
• Droplets fell downwards because of the gravitational force. 
• These falling water droplets on earth are called rains. 
• The water, as vapour goes into the atmosphere by evaporation and transpiration.
• It forms clouds and falls back on earth as rain.
• The water cycle contributes to the deposit of fresh water on the earth.
• This is the most vital fact for the survival of living organisms, as well as the generation of energy. 

Key Terms: Rain, Clouds, Water, Water Cycle, Cloud Formation, Evaporation, Condensations, Transpiration, Sunlight, Moisture, Droplets, Precipitation, Gravitational Force, Earth, Vapour

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Rain

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Rain comprises droplets of water that descend on the earth from clouds. Sunlight heat converts moisture (water) from plants, leaves, oceans, lakes, and rivers into water vapour (gas), which evaporates into the atmosphere. 

• As the vapour rises, cools, and condenses into tiny droplets of water, it forms clouds. 
• Water droplets in the clouds combine to make larger drips.
• The water droplets fall like rain when they become too huge and heavy.

Rain refers to large, heavy droplets that fall to the earth, while drizzle refers to little droplets that fall to the ground. When heavy clouds approach, you know it's going to rain. They are dark because they are full of large water droplets that block out the Sun's light.

• Water is evaporated by biological processes.
• Hot air containing the required water molecules rises above the ground level.
• This hot air is expanded and then cooled after reaching a suitable height.
• The process of converting water vapour into droplets on cooling is called condensation.

Rain

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Causes of Rain

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When there is little cloud cover in the sky, and the sun's rays are at their strongest, heating the earth, water bodies, or vegetation. This causes water to evaporate into the atmosphere.

• The evaporated water condenses and cools, resulting in the formation of a rain cloud.
• This cloud gets denser than air and, as a result, falls to the earth's surface in droplets.
• When the weight of these water droplets becomes too great to keep them floating in the cloud, they descend to earth as rain.

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Importance of Rain

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The importance of rain is as follows:

• Rainwater is the purest kind of water on the earth, and as a result, it is more suitable for drinking.
• We must collect rainwater in order to avoid drought throughout the summer.
• It is the greatest alternative for agricultural applications.
• Rainwater also contributes to the replenishment of our bodies of water.
• It improves the soil's ability to support agriculture.
• Rainwater also contributes to an increase in the volume of groundwater.
• The growth of plants also depends upon rain.
• The rainwater provides water for hydroelectric plants to generate electricity.

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Water Cycle

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The water cycle depicts the ongoing circulation of water within the earth's atmosphere. It is a complex system with many processes.

• Liquid water evaporates into water vapour, condenses into clouds, and falls back to earth as rain and snow.
• In various states, water circulates in the atmosphere through transportation.

Runoff is defined as the passage of liquid water across the land, into the ground (infiltration and percolation), and through the ground (groundwater).

• Groundwater travels into plants (plant uptake) and evaporates into the atmosphere from plants (transpiration).
• Solid ice and snow can spontaneously decompose into a gas by the process of sublimation.
• When water vapour solidifies, the opposite can occur which is called deposition.

Various levels of the water cycle are as follows:

Evaporation

Evaporation is defined as the process when some of the liquid water from lakes, rivers, and oceans turns into vapour. It then travels in the atmosphere with the help of sunlight. 

• Next, the air level rises in the atmosphere and gets cooler.
• In case of less pressure, it is unable to hold much water, so the vapour turns into small water droplets or ice crystals to form a cloud.

Condensation

Condensation is defined as the process of converting water vapour into droplets. The dust particles in the topmost layer of air help in condensation. 

• In this, the nucleus is a term that is used to describe the dust and particles which help in the formation of clouds, thus forming rain.

Formation of Clouds

Clouds are formed when air warms up the Earth’s surface. The formation of clouds takes place when lenticular and stratus clouds are blown into the sides of mountain ranges or terrain by winds.

• Force is moved upward higher in the atmosphere, thus forming clouds.

Water Cycle

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How are Clouds formed?

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Water vapour, an invisible gas, condenses into liquid water droplets to form clouds. These water droplets form on small particles in the air, such as dust.

• The process of cloud formation involves the following steps:

Evaporation 

Evaporation is the process of converting a liquid to a gas. The liquid from oceans, lakes, rivers, swamps, swimming pools–and everywhere is converted into an invisible gas known as water vapour and drifts out towards the atmosphere. 

• When water molecules absorb more energy from a heat source, liquid water transforms into a gas. 
• These energetic molecules subsequently escape as gas from the liquid water. 
• The molecules absorb heat as they change from liquid to gas, which they then release into the atmosphere. 
• This helps to chill the water they leave behind.

Condensation

Condensation is the process of converting gas to a liquid. When a saturated volume of air cools or atmospheric pressure falls, the air can no longer retain all of that water vapour. 

• The process of water changing from a gas to a liquid is known as "condensation." 
• It occurs because of microscopic particles floating in the air, such as dust, salt crystals from sea spray, or even volcanic ash. 
• These particles serve as surfaces for water vapour to condense into liquid droplets or ice crystals.

Freezing

Freezing is the process of converting a liquid to a solid. The process of a gas turning directly into a solid is known as "deposition". Thus, clouds emerge because of these two processes of condensation and deposition.

Point of saturation

Clouds occur when air can no longer carry any more water vapour (gas). This is known as the saturation point. Depending on the temperature and weight of the air–or atmospheric pressure–in a specific place, the air can only hold a fixed amount of water vapour.

• The more water vapour the air can retain, the greater the temperature or atmospheric pressure.
• When a certain volume of air contains all the water vapour it can, it is said to be "saturated".
• Evaporation and condensation, respectively, are used to get saturation.
• Moisture creates visible water droplets as fog and clouds when it reaches saturation.
• Thus, a cloud is a massive concentration of such droplets or ice crystals.

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Things to Remember

• Rainwater is essential for life on earth which refers to large, heavy droplets that fall to the earth.
• The water, as vapour, goes into the atmosphere by evaporation and transpiration, forms clouds, and falls back on earth as rain.
• The evaporated water condenses and cools, resulting in the formation of a rain cloud.
• When the weight of these water droplets becomes too great to keep them floating in the cloud, they descend to earth as rain.
• The process of cloud formation involves various steps like evaporation, condensation, saturation, etc.