Published by: BhumiRaj Timalsina
Published date: 26 Jan 2022
We can see various conditions of the atmosphere. All days are not same. Some days are sunny, some are cloudy and some are rainy. Some days are cold and some days are hot. Sometimes, it may be rainy in the morning and after sometimes, suddenly the sky becomes clear and the day becomes sunny. The condition of the atmosphere can change from hour to hour or day to day or week to week. It does not remain the same. Weather can be defined as the condition of the atmosphere over a short period of time e.g. from day to day or week to week. Weather does not remain the same and it is not same in all the places. It changes from time to time and differs from place to place. Climate can be defined as the average conditions of atmosphere over a longer period of time. Climate describes the long-term weather patterns of a certain area for specified time periods.
When the sun heats the water of the ocean, river, lake, ponds, etc. the water gets evaporated. The vapour then rises up into the sky and mixes with dust particles. The vapour then undergoes condensation and as a result, the cloud is formed. Clouds can be defined as the collection of a tiny droplet of water or ice crystals that floats in the sky. Clouds may be in white or grey colour. The clouds become white in colour when the water droplets in the clouds scatter the light which combines producing a white light. As a result, the clouds looks white in colour. When the clouds become thick, the light coming from the sun are not able to pass through the cloud due to which the cloud looks grey or dark in colour. There are various types of clouds depending on the shape, size, colour and appearance. The main types of clouds are cirrus, cumulus, stratus and nimbus.
As we know that, the cloud is made of very small water droplets or ice crystals. Cloud moves from one place to another. When the cloud gets near to hills, mountains and forest, the cloud gets cooled and changes into rain water droplets which fall down to the earth as a rain. We can see the heavy rainfalls in the month of Asar and Shrawan in Nepal.
Snow simply means small, soft and white pieces of ice that fall from the sky during very cold weather. It is a precipitation in the form of flakes of crystalline water ice that falls from clouds. Snowfall usually occurs in high altitude regions during the winter season. In Nepal, the mountains are covered by snow throughout the air.
Dew is a water in the form of droplets formed due to condensation of water vapours. As we know that the air contains water vapours. The hot air contains more water vapour than cold air. In the night, when the hot air comes in contact with cold surfaces, water vapour present in the air condenses on the cold surface in the form of droplets which are known as dew drops. They are seen mainly in the winter season. The dew formation is seen more when the sky is clear and it is seen less when the sky is full of clouds.But when the temperature becomes further low, the dew changes into ice which is known as frost.
The Earth's atmosphere is air. It is a mixture of various gases like nitrogen, oxygen, water vapour, carbon dioxide, etc. Air is a very important resource. It supplies us oxygen which is very important for us. The air consists about 78% nitrogen, 21% oxygen and less than 1% of argon, carbon dioxide, and other gases with some amounts of water vapour.
The atmosphere is a thick envelope of air that surrounds the earth's crust. It is a mixture of different gases like nitrogen, oxygen, carbon dioxide, etc. It also contains water vapour and dust particles. The amount of gases in the atmosphere goes on decreasing when we move upward from the Earth's surface. The atmosphere is divided into five layers which are discussed below,
The troposphere is the lowest layer that is extended up to 16 km from the earth's surface. It is the layer of air where we live. About 75%- 80% of total mass of atmosphere lies in the troposphere. It contains various gases like nitrogen, oxygen, carbon dioxide etc. All the weather activities like rainfall, cloud formation, lightning, snowfall, hailstones, dew formation etc. The temperature of this layer decreases with increasing altitude.
This is the layer between troposphere and mesosphere. It is extended from 16 km to 50 km vertically upward from the earth's surface. The temperature of this layer goes on increasing as we move upward from the stratosphere. This layer is very dry. It contains very less water vapour. Few clouds are also found in this layer. This layer is also known as a protective layer as it contains ozone layer that absorbs the harmful radiations from the sun and protects living beings on the earth. Commercial jet aircraft fly in the lower stratosphere.
It is the middle layer that lies between stratosphere and thermosphere. It extends from 50 km to 80 km vertically upward from the earth's surface. Temperature decreases as we move upward. A Strong wind blows in this layer.
This is the layer between mesosphere and exosphere. It extends from 80 km to 720 km. The temperature of this layer is very high. The air density is very low in this layer. The temperature in this layer increases as we move upward.
It is the uppermost region of the earth's atmosphere. It is located above 720 km vertically upward from the earth's surface. The air in this layer is extremely thin. There is no clear upper layer of the exosphere as it opens into the outer space.
The fast blowing air is known as the wind. The Wind carries away plastics, leaves, dust particles, etc. A Strong wind can cause huge loss of life and properties. In Nepal, the wind is seen generally in the month of Falgun and Chaitra. As we know that, air is a mixture of various gases like nitrogen, oxygen etc. The molecules of these gases are loosely held together. When they get heat from the sun, they become light and start moving upward. Their place is then occupied by the cold air. This movement of air is known as convection. The Wind blows due to the convection of hot and cold air.
During daytime, the air above the land gets heated faster than the air above the sea. As we know that cold air is heavier than light air. The air above the land becomes lighter and start moving upward. The space of the air of land is then occupied by the cold air that moves from sea to the land. This movement of air is known as the sea breeze.The sea breeze can be defined as the movement of cold air from sea to the land during the daytime. But in the night, the land cools faster than the sea. So, the air above the sea is hot than the air above the land. The air above the sea becomes lighter and the air above the land becomes heavier. Therefore, the air above the sea moves upward and its place is occupied by the cold air that moves from land to the sea. This movement of air is known as a land breeze. Land breeze can be defined as the movement of cold air from land to the sea at night. Land breeze and sea breeze are the reasons behind the constant temperature of land near the sea.