[Physics Class Notes] on Pressure Systems Pdf for Exam

The earth atmosphere has a pressure system that is particularly high or low compared to the air surrounding it. Air expands when noted and gets compressed when cooled. This results in atmospheric variations. Due to the difference in atmospheric pressure, air now starts moving from high pressure to low pressure. The movement of the wind is horizontal, and thereby a constant temperature is maintained on the planet. Pressure systems of the earth are widely divided into two parts: High-pressure system and the low-pressure system. The weather of an area is determined locally by the pressure system. Low-pressure systems bring about clouds and rain while high-pressure systems are responsible for clear skies. 

Explain The High-Pressure System 

The high-pressure system is relative to the air around it. As the air starts becoming warm or cold, it can be said that a high-pressure system has been created. The high-pressure system is composed of air that is heavy and cool. In the high-pressure system, the air is not rising and forming clouds. Therefore the weather remains comfortable, and skies stay clear. In the Northern Hemisphere, the high-pressure system revolves in a clockwise direction, while in the Southern Hemisphere it is in the anti-clockwise direction. 

Explain The Low-Pressure System 

A low-pressure system, commonly known as depression, is created in an area of warm air. As we all know, warm air rises, and cold air falls. The low-pressure system rotation is in the clockwise direction in the Southern Hemisphere and in the opposite direction in the anti-clockwise direction in the northern hemisphere. A low-pressure system brings about heavy rainfall. Depression can often mature into a cyclonic storm in case the low pressure persists. Over the Atlantic Ocean, during the autumn season, the low-pressure system increases, bringing with it windy weather, rain, storms and heavy thundershowers. 

Features of Atmospheric Pressure 

• Atmospheric pressure indicates weather conditions of an area. 

• Low pressure causes cloudiness, thunderstorms, storms and cyclonic winds.

• High pressure contributes to calm weather conditions. 

• An instrument known as the barometer measures atmospheric pressure. Therefore the barometer is also known as barometric pressure. 

• One atmosphere is 1013 millibars or 760 millimetres. 

The atmospheric pressure is an important environmental factor. It affects all the three states of matter that are solid, liquid and gas. This atmospheric parameter has been used quite a number of years to predict weather conditions all over the world. The composition of water and its chemistry is also affected by atmospheric or barometric pressure. The earth’s atmosphere has five layers. From highest to lowest they are:

1. Exosphere

2. Thermosphere 

3. Mesosphere

4. Stratosphere 

5. Troposphere 

Each of these layers extends up to an absolute mile and are above sea level. The exosphere is about 700 km above sea level while the average height of the troposphere is near about 18 km in the tropical regions and 6-7 km in the polar region. In various images, the different atmospheric layers are shown in different colours. Each of these layers has a different temperature and pressure levels. 

Solved Examples

1. Difference between High and Low Pressure Systems.

A low-pressure system has slight pressure in the area of the suit and its centre. The wind blows towards the low-pressure areas, and the air rises in the atmosphere as soon as they meet. Once the air rises, clouds are formed, leading to precipitation. On weather maps and meteorological departments, a low-pressure area is marked with an L. 

A high-pressure system has pressure in its centre and the surroundings. In a high-pressure system, the winds blow in an anticyclonic manner. This results in the air from the higher atmosphere to fill the spaces left in the outward. On a weather map, you might notice a high-pressure system marked as H. 

Fun Facts

• The readings of a pressure system are given in millibars. 

• Places having equal air pressure are connected by lines known as Isobars. Sea level pressure has an average of around 1013 millibars. 

• Any changes in the air pressure will accordingly determine the weather of a localised area. 

• As air pressure increases the weather becomes clearer while falling air pressure leads to storms.

• Pressure readings are usually relative to that of the area. There is no scale or division of the air pressure range.