[Biology Class Notes] on Rain Pdf for Exam

The water cycle is one of the most important natural processes that help in the circulation of water all through the soil and air in the form of rain and snow, drainage and evaporation as well as precipitation. The processes of nature are always in balance, and this is why these cycles play such an important role in regulating the Earth’s climate. 

Rain is one of the most common ways through which water is added back into the soil from the atmosphere. These natural processes need to be in sync so that the ecological balance does not go out of hand. 

What is Rain?

Rain is droplets of water in the form of liquid which are condensed from water vapour present in the atmosphere and fall down on the ground under gravity when they become heavy. It is the major component of the water cycle process and helps in depositing fresh water on the Earth which is essential for living organisms for survival, producing electricity via hydroelectric power plants and irrigating crops. 

Rain is nothing but the condensed water from the atmosphere becoming too heavy to stay in the air any longer. It falls from clouds back into the earth, seeps into the soil and starts the rain cycle all over again. 

Explaining the Water Cycle

Consider water that is available in the soil at the surface. When the sun shines, the heat from the sun makes this water turn into vapour. The water becomes light and thus, it gets evaporated and slowly finds its way into the atmosphere from the soil. 

Once it starts getting away from the soil, the temperature starts to cool down. This makes the water vapour turn heavier than it was when it evaporated. The cool temperature then turns clusters of these water vapour particles into clouds, which is known as condensation. 

Clouds grow in size until they are too big and too heavy to contain all the condensation. In that case, the water falls back as rain into the soil, the resultant process being known as precipitation. Therefore, the cycle essentially never breaks and continues through time. 

What are the Various Processes of the Water Cycle?

As we have explained here, every step of the water cycle is accompanied by a natural process that deals with water turning to vapour or to liquid. The following processes are involved in the water cycle mainly: 

1. Evaporation

It is the process where some of the liquid water from lakes, rivers and ocean turns into vapour and travels in the atmosphere, with the help of sunlight. The air rises in the atmosphere and gets cooler and under less pressure, it is unable to hold much water so the vapour turns into small water droplets or ice crystals to form a cloud.

2.  Condensation

The dust and pollen particles present in the topmost air help in condensation where water vapours condense into water droplets .Condensation nuclei is a term used to describe the dust, pollen or other particles that assist in forming clouds and in the process of rain.

3. Formation of Clouds in Different Ways

• Some clouds form when air warms up near the Earth’s surface and rises. The heat by sunshine helps in heating the ground and air just above it that starts to rise and form clouds.

• Some clouds known as lenticular and stratus clouds are formed when wind is blown into the sides of mountain range or terrain and it is forced upward to move higher in the atmosphere. This aids in forming clouds.

• Some clouds form when the air is forced upward at low pressure areas. This process leads to the formation of all types of clouds including altocumulus, cirrocumulus, altostratus, cirrocumulus and stratus clouds.

Why is Rain Important? 

The importance of water and the proper working of the water cycle is of utmost importance, because it can lead to significant ecological changes even if thrown off-balance a little bit. Rainfall is very important because: 

• Plants grow with the help of rain showers. No plant will be able to grow without water from rain.

• Rain is the major component of the water cycle that helps in depositing most of the freshwater on the Earth. It supports many types of ecosystems and helps in survival.

• It provides water for hydroelectric plants to generate electricity.

• It is very helpful for crops to grow as it is a means of crop irrigation on the large fields.

• It helps in sustaining water level in the ground.

• Humans make use of the rain water to store and later use it for bathing, cooking, cleaning and drinking. It is called rain harvesting. This process helps in reducing water bills as it provides an alternative supply of water during restrictions and also maintains a healthy and clean garden. There are various filtering options to clean up rain water for direct usage.

• Rain helps in cooling the atmosphere and helps in reducing the intense temperature of the Earth. Therefore, it is a great relief when it rains during the Summer season.

• It helps in humidifying the air and replenishing the water table.

• It helps in generating healthy negative ions.

• It redistributes the fresh water via a water cycle.

• We can enjoy the beauty of rain when it is just drizzling.

• It is one of the most important natural phenomena that makes life possible on Earth as agriculture and forest depend on rain which are ultimately the basic requirements for humans. Thus, it helps in generating food as well as supplying water.