Let us learn about the factors affecting atmospheric pressure.

What is Atmospheric Pressure?

Since air is a physical substance, it must exert some force on the earth's surface. Instead of measuring the force, we measure the force per unit area. And so the force per unit area exerted by the weight of the air on the unit area of the earth is called Atmospheric Pressure.

What are the factors affecting Atmospheric Pressure?

Do you think the air pressure in mountains and the air pressure inside a sea are the same?

Factors affecting Atmospheric pressure

Like other elements of weather, pressure also varies from place to place and time to time. The most important factors affecting the distribution of pressure are as follows:

1. Altitude

At hill station, have you seen that you get out of breath very fast? What does this suggest? This suggests that the density of air at higher altitudes is less than that at sea level. The maximum air density is at the earth's surface. When air rises, the molecules get farther apart and outward pressure decreases, whereas in lower layers, in a compressed state, the molecules of air get closer together and outward pressure increases.

Basically, atmospheric pressure has an inverse relationship with height. It decreases with an increase in altitude. The decrease of pressure is about 1 cm of mercury for every 110 m of ascent.

2. Temperature

Temperature is inversely proportional to pressure. It is because, with the rise in temperature, the air gets heated up and rises. On the other hand, when the temperature is low, the air becomes heavier and denser. This is the reason the Equatorial region has a low-pressure belt while the Polar regions have high-pressure belts.

3. Water Vapor

Atmospheric pressure varies with the amount of water vapor in the air. Do you know why? Water vapor concentration affects atmospheric pressure because the molecular weight of water (18g/mol) is less than the average molecular weight of air (29g/mol). When water evaporates and enters the atmosphere as a gas, it takes place of other gas molecules.

4. Rotation of Earth

Due to the rotation of Earth, the bulk of the air at the poles is thrown away towards the Equator. Since the Equatorial region receives a great amount of heat throughout the year, the air becomes warm and light and therefore it rises and creates low pressure. At the poles, the cold heavy air sinks down and creates high pressure. In fact, temperature and rotation together contribute to the formation of the world pressure belts.

Do you know which forces are produced by the rotation of Earth?

Earth's rotation produces the Coriolis force, which tends to turn the flow of air. This effect is absent at the Equator and increases as we go towards Poles. These factors make air pressure an important parameter in predicting the weather. In general, weather becomes stormy when air pressure falls and becomes fair when air pressure rises.

Factors Affecting Atmospheric Pressure Questions

1. Which force is a direct result of the rotation of the Earth?
(i) Gravitational force
(ii) Magnetic force
(iii) Electromagnetic force
(iv) Coriolis Force

2. Which of the following has comparatively more air pressure compared to the rest?
(i) Japan
(ii) South America
(iii) Africa
(iv) Antarctica

3. Which factors contribute to the formation of the world pressure belt?
(i) Altitude and Temperature
(ii) Rotation and Altitude
(iii) Water vapor and Altitude
(iv) Temperature and Rotation of Earth

4. Which part of the Earth has maximum density?
(i) Core
(ii) Crust
(iii) Mantle
(iv) Surface

5. What is the decrease in pressure for every 110 m of ascent?
(i) 1.5 cm of mercury
(ii) 1 cm of mercury
(iii) 1.2 cm of mercury
(iv) 1 cm of mercury

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