[Geography Notes] on Atmospheric Pressure Pdf for Exam

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.

2. 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.