Science Facts

How Do Air Move? – Causes, Mechanism & Effects

Air movement

Air is a mixture of gases in constant motion. Differences in air temperatures create winds. The air has many gases in it, about eight-tenths of the air is nitrogen (78%), and about two-tenths are oxygen (21%). A tiny part of the air is carbon dioxide, water vapor, and other gases. No different planet in this solar system has air like Earth’s.

The average atmospheric pressure on Earth is 1 bar (100,000 Pascals). But luckily, that pressure isn’t pushing straight down. The force goes out in all directions. The Earth is rotating, and the atmosphere isn’t attached to Earth. That causes the wind to curl and rotate. It is known as the Coriolis Effect. The mixture of pressure and temperature with a rotating Earth tilted on its axis and covered in sun-absorbing landmasses. As a result, the winds of the Earth begin to swirl like a Van Gogh painting.

Why does air move?

We cannot see the air moving, but we can feel it and see its effects when it moves objects. The whirlwind effect causes heat and air in motion. Air is everywhere, all the time. But where exactly does it come from? The air molecules are bouncing around and colliding with each other. It creates a force, and it’s the force of all those bouncing air molecules over a given area of Earth that results in pressure. Also, the air has mass, and gravity drives that air down towards the ground.

The uneven heating of the atmosphere causes the movement of air that results in diverse types of atmospheric phenomena in different regions of the Earth. As mountain ranges, Earth’s rotation plays a significant role in causing the diverse atmospheric phenomenon. The Himalayas play an essential role in changing the direction of monsoon Vince.

How do air move?

The movement of air winds and the weather conditions of the environment do not remain the same during the entire day or year. Sometimes there is a cool evening breeze after a hard day. Days are having strong winds or terrible storms after some days of hot weather. All these phenomena happen in the atmosphere due to the heating of air and the formation of water vapor. Water vapor is formed due to the evaporation of water from the surface of the water bodies.

Water vapor is also formed due to transpiration by plants and precipitation by animals. The heating of the atmosphere by radiation accelerates the process of evaporation. The atmosphere is also heated from below by the radiation reflected or radiated by the land of bodies. On heating, the air present near the earth’s surface rises, creating an area of low pressure. As a result, convection currents are set up in the air.

Air movement in coastal regions: In the coastal areas, the air about the land gets heated faster than the air over the sea. The heated air over the land rises and creates a region of low pressure. As a result, the air over the ocean moves towards the coast to land. The movement of air from one region to the other creates winds. Thus the direction of the wind would be from the sea to the land during the daytime. After the sunset, both land and sea start to cool. The water cools slower than the land. Consequently, the air about water would be warmer than the air about land. This would cause blowing off wind from land to the sea.

Movement of air in the atmosphere: There are five layers in the Earth’s atmosphere. Most weather conditions only happen in the bottom layer of the troposphere as you go up through the five layers, temperatures, and air pressure change. Air pressure decreases at high altitudes through the atmosphere. The troposphere is about 10 miles high, and this is where weather happens.

The composition for weather:

  • Temperature
  • Pressure
  • Volume and density.

The combination of all these ingredients in the troposphere creates different kinds of weather. Air pressure decreases as you move up higher. This decrease happens because the gas particles in the air get farther apart and less air above on earth. The different temperatures also cause convection currents to form. In a convection current, gases or liquids rise and sink in a circular path.

As cool air moves under warm air, the wind is created. Wind occurs as air moves from high air pressure to a place of low air pressure. In the cool air, gas particles are closer together than in warm air. It means that every liter of cool air is heavier than every liter of warm air. When the two kinds of air are next, the cool air will sink and force the warm air to rise.

Six huge convection currents form in the air earth. One reason they form is that tropical regions get warm more than other parts of the earth. Warm air from tropical areas rises. After they are cooled, it sinks further north and south. The huge convection currents’ move combines with the earth’s spinning to cause regional surface wind patterns. Winds generally move from west to east over much of the United States.

Jet streams are high above the ground between the huge convection currents. A jet stream is a band or a high-speed wind formed by different temperatures between the conduction currents. Even though it is very high, a jet stream affects air movement changes in temperature, winds, and precipitation.

Air movement mechanism

The boundary where two air masses with different properties meet is called a frontal surface. And the border where a frontal surface meets the ground is called a front. A front is a line where cold or hot air meets the ground’s surface in simpler terms. Depending on how the cold air and warm air meet, it can be divided into cold fronts and warm fronts.

  • When a front passes through an area, weather changes occur on either side of the front.
  • When a cold front passes over land, air temperatures drop, the air pressure rises.

Behind a cold front, cumulus clouds form, resulting in showers concentrated over a small area. When a warm front passes over land, air temperatures rise, the air pressure drops, and stratus clouds form, with light sprinkles of rain over a broad area. There are also occluded fronts and stationary fronts. Cold fronts move quickly, while warm fronts move slowly.

  • When a cold front and a warm front are moving in the same direction, the faster cold front catches up to the warm front. And a new front form where the two fronts overlap. This is called an occluded front.

A stationary front occurs when neither of the two air masses is strong enough to push the other one out of the way. This front does not move very much and stays in the same place for a long time. If there are torrential rains at the front, then the front is called a rain front. This is an example of a weather map that we see on the news every morning.

On this weather map, points where the air pressure is a line has connected the same called an ‘isobaric line.’ Places with higher air pressure than the surrounding areas are marked High (H), and low-pressure areas are marked Low (L). Around low-pressure areas, rising air currents form, and in high air pressure areas, falling air currents form.

In low-pressure areas, moisture-laden air rises and forms clouds, resulting in cloudy, rainy, or snowy weather. And around high-pressure areas, the air descends, making it difficult for clouds to form. This results in clear weather.

High-pressure zones are divided into ‘stationary’ high-pressure zones, which remain in one place with minimal movement, and ‘migratory’ high-pressure zones. It separates from the stationary high-pressure zones and moves with westerly winds. The Siberian high-pressure zone, which affects Korea in the winter, and the North Pacific high-pressure zone, which affects Korea in the summer, are stationary high-pressure zones.

Meanwhile, low-pressure zones can be divided into ‘temperate’ low-pressure zones and ‘tropical’ low-pressure zones, depending on where they occur. Temperate low-pressure zones occur at cold fronts around 60 degrees latitude. First, cold air and warm air meet to form a stationary front. Temperature differences between the air cause ripples. And the rotation of the Earth causes the low-pressure systems to move in a counterclockwise direction. Cold fronts and warm fronts form at the center of the low-pressure zone.

First, stratus clouds form ahead of a temperate front, with light sprinkles of rain over a broad area. There are almost no clouds between a cold front and a warm front, resulting in clear weather and hot air temperatures. Behind a cold front, cumulus clouds form, resulting in showers concentrated over a small area. Temperate low-pressure zones ride westerly winds and move from west to east. This is why a person located to the right of a temperate low-pressure zone can view weather patterns preceding a warm front, between different fronts, and behind cold fronts.

Lastly, the cold fronts move faster than the warm fronts, causing the fronts to overlap and form occluded fronts. As the warm air rises above the cold air and stabilizes, the low-pressure temperature zone disappears. It takes around 5 to 7 days for a temperate low-pressure zone to disappear.

Effects of air movement

Air influences our lives in many ways and causes various meteorological phenomena. Snow, rain, and wind are just some of the phenomena created by wind. These weather patterns vary depending on the pressure of the air. It is difficult to tell since it has no color and smell, but air varies in temperature and humidity.

A large body of air with the same temperature and humidity is called an ‘air mass.’ The air mass temperature depends on its North-South location, also known as its latitude position. Air masses at low latitudes are close to the Equator and are therefore warm or hot, and those at higher latitudes are cold. Also, air masses that form out at sea suck up moisture from the water, making the air humid. Over continents, air masses are dry.

Air in motion is significant.

  • Moving air helps flowers to make new flowers through pollination.
  • Air can help a sailboat to move faster.
  • Fast-moving air can also make energy.

Next, we have tropical depressions. These have different names depending on where they occur. In Korea and Southeast Asia, tropical depressions are called typhoons. Around the Atlantic, they are called hurricanes. In other places, a tropical depression is known as a cyclone. Generally, a typhoon is a tropical depression where the maximum wind speed near the center is 17 meters per second or greater. The diameter of a typhoon can vary from 200 km to 1,500 km, and the average height of a typhoon is around 15 km.


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Sources:

ASHRAE, ed. ASHRAE Handbook of Fundamentals. Atlanta, GA: American Society of Heating, Air-Conditioning, and Refrigeration Engineers.
“Aerodynamics – Introduction to the science of air flow.” Explain that Stuff.
Axley, James W. “Residential Passive Ventilation Systems: Evaluation and Design.” Air Infiltration and Ventilation Center.
Schiavon, Stefano. “Adventitious ventilation: a new definition for an old mode?”.
Toftum, J. “Air movement – good or bad?”. Indoor Air.

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