Atmospheric Pressure

What is Atmospheric Pressure?

Depending upon the gravitational pull of the earth, atmospheric pressure can be defined as a force exerted upon a surface by the atmospheric column. There are various units of measuring atmospheric pressure, including millimeters of mercury, psi, millibars, kilopascals, and dynes per square centimeter. Barometers consist of a mercury column in a glass tube that is commonly used to measure it. Changing the weight of the atmosphere with the rise or fall of the mercury level lets us analyze the change in atmospheric pressure.

Earth's weather and climate are influenced by both atmospheric pressure and wind, which are known as the Earth's controlling factors. Despite having different physical characteristics, atmospheric pressure and wind are closely related. 

Students can use the information in this study guide to prepare for any exam since we have provided an overview of the pressure and wind systems. Also, this article will help them understand the relationship between atmospheric pressure and temperature.

What is a Pressure System?

According to the definition of a pressure system, an area of the Earth's atmosphere is defined by the rise and fall of its pressure. When compared to the surrounding air, the pressure in this region is unusually high or low. All of these phenomena collectively are called the pressure system.

As a result of atmospheric pressure differences, air constantly moves from high to low pressure. Due to the expansion and contraction of the air in response to heating and cooling, this difference occurs.

Parts of the Pressure System

There are two parts to the pressure system

  1. High-Pressure System:

Light winds are associated with high-pressure systems beneath the surface, and subsidence is associated with high-pressure systems lower in the atmosphere. As a result of adiabatic or compressional heating, subsidence dries out an air mass. Consequently, high pressure usually corresponds to clear skies. The daytime temperature rises because there are no clouds to block the shortwave solar radiation. Since there are no clouds at night, longwave radiation is not absorbed and low temperatures are cooler during all seasons. When compared to a low-pressure system, a high-pressure system swirls the other way. This flow pattern is referred to as anticyclonic.

  1. Low-Pressure System:

An area of low atmospheric pressure is one in which the pressure at sea level is lower than that at other nearby locations. The tropospheric upper levels experience areas of wind divergence, which leads to low-pressure systems.

The formation of a low-pressure system occurs when a desert or other landmass is heated up by greater sunlight. Since the warm air in localized areas is less dense than the surroundings, the warm air rises, lowering the atmospheric pressure. Monsoon circulation is influenced by pressure gradients created by large-scale thermal lows over continents. In low-pressure systems, the wind swirls counterclockwise because Earth spins and the Coriolis effect applies. The category in which this occurs is cyclonic.

Around the globe, low-pressure systems tend to develop over the Tibetan Plateau and the southern slopes of the Rocky Mountains. Known as depressions in Europe, low-pressure weather systems recur over a long period.

Millibars are the most common unit of measurement for these pressure systems. Everybody knows how important the atmosphere is. Weather conditions in particular regions are affected by this factor. An increase in air pressure alters the weather conditions accordingly. Whenever the air pressure increases, the weather becomes clearer, whereas when the air pressure falls, storms occur and the skies are cloudy.

Relationship Between Atmospheric Pressure and Temperature

In direct proportion to each other, atmospheric pressure and temperature are highly related. Temperature increases cause atmospheric pressure to rise as well, and vice versa.

In accordance with Gay-Lussac's Law, the product of an initial pressure (P1) and an initial temperature (T1) is equal to the product of a final pressure (P2) and a final temperature (T2). 

Mathematically, it is written as P1T1=P2T2 

Let's examine car tires as an example to understand the relationship better. As the temperature rises during summer, the molecules of air move and occupy more space, resulting in an increase in atmospheric pressure. During winter, the air molecules move slowly and are not as active, thus taking up less space — a less dense atmosphere results.

The Effect of Atmospheric Pressure and Temperature in Terms of Geography:

The atmospheric pressure decreases when the temperature of a place increases. Temperature increases result in heat being emitted from the air.  The warm air expands. Since the molecules in the warm air become lighter, there is less force exerted on them. The opposite happens when the temperature drops, cooling the air and making it dense. As a result, a high-pressure area is formed.

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FAQs (Frequently Asked Questions)

1. What does atmospheric pressure mean?

At any given point on Earth, atmospheric pressure is the product of the mass of the atmospheric column of the unit area above the point and the gravitational acceleration at the point. Historically, standard atmospheric pressure has been defined as what would be exerted by a standard column of mercury 29.92 inches (760 mm) high or 1013 millibars (101.3 kilopascals).

2. What are the applications of atmospheric pressure?

Syringe: Pulling up on the piston will decrease the atmospheric pressure inside the cylinder. In the syringe, the liquid is pushed upward by atmospheric pressure.

Straw: The pressure inside the straw becomes low when a person suckers through it. Outside, where there is higher atmospheric pressure, water will force its way into the straw leading to a mess in the mouth.

Vacuum Cleaner: Vacuum cleaners suck out air when they are turned on, causing the pressure inside to decrease. The air and dust particles are forced into the cleaner by atmospheric pressure, which is higher in magnitude.

3. How do you define atmospheric pressure? How is atmospheric pressure caused?

As gravity pulls the Earth toward the surface, atmospheric pressure forces an object against its surface. In literal terms, atmospheric pressure is the weight of the atmosphere at sea level. As a result of the atmosphere pushing downward on itself and on the surface below it, it causes this phenomenon.

4. How is it that the huge pressure exerted by the atmosphere does not crush our bodies?

Our body and the atmosphere are in balance when the atmospheric pressure pushes towards us and the blood pressure pushes away from us. Our body's internal pressure differs from our external atmospheric pressure, so we can burst into space if our blood pressure is high. Because the body pressure and the atmospheric pressure are equal, our bodies are not crushed by the atmospheric pressure.

5. Why does atmospheric pressure decrease as we rise higher above the earth's surface?

At any given altitude, pressure can be interpreted as the total weight of the air above a unit area. At first, the air pressure decreases rapidly due to the force of gravity, then more slowly at higher levels as the molecules are held closer to the earth's surface because of the force of gravity.

6. How Does Wind Form?

The formation of wind occurs when there is a difference in atmospheric pressure of two different areas of the Earth's surface. The wind is thus the movement of air from a high-pressure area to a low-pressure area and is caused due to the uneven heating of the earth's surface.

7. What are Surface Winds?

The winds that surround the surface of the Earth and play a significant role in controlling the weather conditions of an area are known as surface winds. The speed of the surface winds can be measured with the help of an anemometer.