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Movement of air can be defined as the changes that take place in our atmosphere that are caused by the differences in water vapour, pressure and temperature. It is also called wind. The movement of air across the earth determines the weather and climate of all regions. Wind is a phenomenon that is the result of various changes that occur in our atmosphere like heating of air and the formation of water vapour. Atmosphere is like a blanket covering the earth. It plays an important role in climate control which directly or indirectly affect the movement of air.
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Key Terms: Wind, air pressure, water vapour, temperature, heat, precipitation
What Causes Movement of Air?
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Temperature, water vapour and Pressure are the main reasons behind the movement of air. The heat emitted by the sun heats up the land and the water bodies. The land and the water bodies reflect this heat back into the atmosphere, thus making the air less dense. This leads to the increase of hot air in the atmosphere and creates a low pressure in that particular region. As the pressure decreases, the cold air starts settling down and creates a region of high pressure.
Thus, for maintaining equal pressure in the air, the cold air from the high pressure regions flow in the direction of low pressure regions resulting in the movement of air, i.e., winds.
What Causes Movement of Air?
Factors affecting the Movement of Air
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1. Pressure
Air pressure plays an important role in the movement of the air. When there is a difference of pressure between regions it leads to the formation of a pressure gradient which allows the air to move from high pressure region to low pressure region. As air doesn’t follow a straight path, this movement of air takes place in an outward direction that is from high pressure to low pressure.
The main reason for this pressure is the rotation of earth beneath the earth that causes an apparent deflection of the wind to the right in the northern hemisphere and left in the southern hemisphere.
Pressure and Movement of Air
2. Temperature
Difference in temperature is another factor that affects the movement of air. Due to the radiation emitted by the sun, the air near the surface of the land gets heated. This heated air being lighter than the surrounding air starts expanding and rising. This movement of air from warmer regions near the earth's surface to the higher surface up in the atmosphere is known as convection. It is the vertical movement of the air. This vertical lift of air also leads to the formation of clouds which after undergoing the process of water cycle gives us rain.
Different surfaces heat up differently resulting in different movement of air everywhere. Example, the area near the sea gets heated quickly due to the heating of seawater. Whereas, a grassland takes much longer to heat.
3. Weather and Climate
In summer, as the land heats up faster than the sea, a region of low pressure is created. Due to low pressure, the air rises and a movement of hot air is created in the atmosphere. This usually leads to cloudiness and precipitation.
During monsoons, air traveling from one place to another contains moisture and water vapor, which when stuck at a mountain range results in the formation of rain. A monsoon is a type of seasonal wind as it changes the direction between summer and winter. Whereas in winter, the land begins to cool quickly compared to the ocean and air begins to flow back to the sea. This air, however, is dry since it has lost all its moisture over land.
Role of Weather and Climate on Movement of Air
Things to Remember
- Temperature and pressure and the main factors that cause the movement of air.
- The vertical movement of the air is called convection and the horizontal movement of air is called as advection.
- Low pressure usually leads to cloudiness and precipitation. Whereas, high pressure leads to fair and calm weather.
- Air is a bad conductor of heat.
- The land near the sea gets heated faster as compared to an open grassland.
- Uneven heating of air over land and water-bodies causes winds.
Sample Questions
Ques. What Causes Winds? (2 marks)
Answer: The uneven heating of the Earth's surface causes winds. When air is heated, it becomes lighter and rises in the atmosphere. As a consequence, a low-pressure area is formed. The air then travels from a high-pressure area to a low-pressure area, causing winds.
Ques. How are Clouds Formed? (3 marks)
Answer: Due to the heat radiated from the sun, a huge volume of water evaporates from various water bodies during the day and rises into the air. As a result of this, the air in the atmosphere heats up. When water vapour-carrying air rises, it expands and cools. Water droplets develop as a result of the condensation of water vapour. Clouds arise as a result of the production of water droplets.
Ques. How Does the Atmosphere Act as a Blanket? (2 marks)
Answer: The atmosphere keeps the temperature of the Earth constant. It avoids a sudden increase in the temperature during the daytime due to the sun. It blocks or slows down the escape of heat from the Earth into outer space during the night- time. Thus, the atmosphere acts as a blanket and shields us from all the excess heat and radiation.
Ques. List any four activities that lead to air pollution. (2 marks)
Answer: Human activities that would lead to air pollution are:
- Deforestation
- Automobile emissions
- Industrialisation
- Combustion of fossil fuels.
Ques. What is the effect of Moving Air? (3 marks)
Answer: The moving nature of air and water is responsible for the smooth running of life on earth. All those water and air movements happen according to changes in temperature, the earth’s rotation around the sun as well as itself and its position from the sun. Though, too much moving air can be disastrous. It can cause storms, heavy winds, etc.
Ques. How does Air Pressure affect Wind? (2 marks)
Answer: Wind is caused by differences in air pressure within our atmosphere. Air under high pressure moves toward areas of low pressure. The greater the difference in pressure, the faster the wind flows.
Ques. What are the two forms of oxygen found in the atmosphere? (2 marks)
Answer: A diatomic molecular form (O2) and a triatomic molecular form (O3) of oxygen are present in the environment (O3 known as ozone).
Ques. Why is the Atmosphere essential for life? (2 marks)
Answer: The atmosphere maintains the Earth's average temperature fairly constant throughout the day and even throughout the year. In the daytime, the atmosphere prevents a rapid rise in temperature. Whereas, it reduces the amount of heat that escapes into space throughout the night.
Ques. What is the effect of pressure on the movement of Air? (2 marks)
Answer: Air moves from place to place because of pressure. The more the pressure difference is, the more air’s movement will be. In other words, the wind or air travels when a pressure gradient is developed. This pressure gradient comes into being when one region has high pressure, and the other has low pressure. Wind tends to travel from the high-pressure land to the low-pressure land. So, the effect of pressure on the movement of Air is massive.
Ques. What is the effect of temperature on the movement of Air?(2 marks)
Answer: The effect of temperature on the movement of Air is similar to the effect of pressure on it. As the difference of temperatures between any two zones increases, the air moves faster between these two regions, and when the temperature difference decreases, the air stops moving. This is because the increase in the temperature causes the particles of air to expand and move faster as they get heat energy from the surrounding.
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