When you are standing and looking through the atmosphere, you may not see anything as we live at the bottom of the atmosphere. But there is a lot of air around us. Air pressure is known as the weight of the air above us. It can be high or low pressure.
High Pressure vs Low Pressure
The main difference between high pressure and low pressure is the circulation that surrounds them. In low pressure, there is a rise in the air and it cools down. The moisture condenses which causes clouds. Whereas in high pressure the air starts to sink and it warms up. The clouds evaporate.
In high pressure, which is also known as an anticyclone, the winds are light and circulate in a clockwise direction. This means they blow in the northern hemisphere. There is a reduction in cloud formation as the air is descending and the weather condition settles. The air also warms up.
In low pressure, which is also known as depression, the air starts rising and circulates in an anti-clockwise direction. This means it blows around the low. The air gets cooler and water vapor condenses which is the cause for clouds to appear. The weather is often unsettled in a depression.
Comparison Table Between High Pressure and Low Pressure
| Parameters of Comparison | High Pressure | Low Pressure |
| Definition | During high pressure, the atmospheric pressure is more than that of its surrounding area. | During low pressure, the atmospheric pressure is less than that of its surrounding area. |
| Condition of Air | The air sinks and becomes warm. | The air rises up and becomes cool. |
| Movement | Clockwise direction. | Anti-clockwise direction. |
| Weather quality | The weather conditions settles up and there are no clouds so the sky clear up. | The weather is usually unsettled with rapid increase in cloud formation which leads to precipitation of rain. |
| Other name | Anticyclone | Depression |
What Is High Pressure?
A high-pressure area is where the atmospheric pressure is more than its surrounding environment. Such areas where the pressure is above average are known as anticyclones. This happens when the air is sinking and as a result, the clouds begin to disappear. Winds within such areas flow outward near their centers towards the low-pressure areas. The winds are light and blow in the northern hemisphere, in the clockwise direction.
The weather in a winter anticyclone
In winters, there are no clouds in the sky, so the heat easily escapes. Therefore, there is very cold temperature and the ground cools down during the night. The formation of fog is seen as the air makes water vapor condense. It lasts for a long time and continue during the day due to less heat from the sun. The water droplets that form gradually evaporate away.
The weather in a summer anticyclone
In summer anticyclones, the weather is very different. The air descends, there is heat which causes the water to evaporate in the air. There are very few clouds in the air and the sky gets cleared up. This allows the sun rays to reach the surface of the earth and the temperature rises.
What Is Low Pressure?
A low-Pressure area is a region that has lower atmospheric pressure than its surrounding areas. Usually, it takes place in the mid-latitude temperature zones and the process is known as cyclogenesis. The formation process has four stages-
- The first one is the early stage.
- Then comes the mature stage.
- The third one is the decay stage.
- And lastly, the dissipation stage.
Seven days is the average life expectancy of a low-pressure area. A low-pressure system has lower pressure at its center and the winds blow towards it. The air rises, causing the water vapor to condense.
Weather in the winters
During the winter season, the conditions are usually stormy or wintry. The position of a jet stream is further south than what is in the summer. This means that the weather is unsettled and some possible conditions are frontal snowfall, heavy rain, storms, and floods.
Weather in the summers
During the summer season, low pressure can lead to prolonged rainfall. Sometimes in extreme conditions, floods may also occur which can cause chaos. However, in-between weather fronts, it is still possible to get a clear sky when the sun comes out. Some unsettled conditions during this time are flash floods, storms, and heavy rain.
Main Differences Between High and Low Pressure
- In high pressure, the air starts sinking and the winds are light, whereas in low pressure the air rises, and the wind blows hard.
- The wind blows in a clockwise direction during high pressure and on the other hand in low pressure, it blows in an anti-clockwise direction.
- During high pressure, the cloud formation starts to reduce as the air descends. But during low pressure, the clouds appear as the water vapor condenses.
- The air cools down in high-pressure areas, whereas it warms up in low-pressure areas.
- The high pressure is known as anticyclone and the weather is different in both summer and winter. On the other hand, low pressure is known as depression.
- The weather conditions usually settle up in high pressure whereas the conditions are unsettled in low pressure.
Conclusion
Above each square inch of the earth’s surface, there are 14.7 pounds of air. This means that air exerts 14.7 pounds of pressure on the surface of the earth. Air pressure decreases in the high atmosphere. As the air molecules are few, the pressure is less from the weight of the air above. Every day the pressure varies at the bottom of the atmosphere because the earth is not equally heated by the sun.
When high and low-pressure systems are formed, they tend to change the height of the atmosphere. The airflow is shown by the cross-section of the two systems. In a high-pressure system, there is more atmosphere on the ground. This is where the high pressure comes from and the opposite occurs in low pressure. A low-pressure system works when hair gets heated by contact with a water mass. Therefore the pressure changes with various factors.
Reference
- https://www.nature.com/articles/nmat716
- https://science.sciencemag.org/content/241/4868/913.extract