Atmospheric Disturbance

Atmospheric disturbance refers to the phenomenon which includes a closed circulation of air around a low pressure which is created at the centre and a high pressure that is created at the periphery. The air rotates anticlockwise in the northern hemisphere and clockwise in the southern hemisphere. This circulation of air with lower pressure in the centre and higher pressure in the periphery is called a cyclone. 

Atmospheric Disturbance

As mentioned earlier, a cyclone is the circulation of air with low pressure in the centre and high pressure in the periphery. A cyclone and an anticyclone are two components of atmospheric disturbances. On the basis of their origin, cyclones are divided into two categories: These two categories are called 1) tropical cyclones and 2) temperate cyclones. 

Tropical Cyclones: Tropical cyclones are created in lower latitudes, commonly known as the tropics. These types of cyclones do originate over warm ocean waters. As the warm air rises, it causes a region of low pressure. At first, a tropical disturbance is created. A tropical disturbance or tropical depression creates low wind speeds of 31 to 61 km per hour. A tropical cyclone which has a speed of 62 to 88 km per hour is usually assigned a name. The cyclones that are considered severe cyclones usually have a wind speed of 89 to 118 km per hour. Very severe cyclones have wind speeds of 119 to 221 km per hour. Super cyclones have wind speeds that exceed 221 km per hour. 

The origin of tropical cyclones depends on certain conditions. These conditions are, 

A source of warm, moist air that is derived from the tropical ocean. The average surface temperature of the ocean is around 27 degrees Celsius.

Wind near the ocean surface blows from different directions. The winds converge on each other, and this convergence causes the air to rise and form storm clouds. 

Winds that don’t vary greatly with height are known as “low wind shear.” This allows the storm clouds to reach high levels vertically. 

The earth induces a unique kind of attraction force called the Coriolis force. When a cluster of storm clouds starts to rotate, a tropical depression is created, and if this development continues, it creates a tropical storm. It can later develop into a cyclone or super cyclone. 

Characteristics of atmospheric disturbances

One of the most common atmospheric disturbances is the tropical cyclone. The key characteristics of tropical cyclones are:

The centre of the cyclone, where low pressure is centred and the wind converges and rises, is called the “eye.” The eye region doesn’t experience any rainfall, but it experiences the highest temperature and lowest pressure. 

The cyclone wall consists of cumulonimbus clouds. These clouds have no visibility, high wind velocity, and cause heavy rainfall with lightning and thunder. 

Tropical cyclones mostly move along the path of the trade winds. So it is evident that tropical cyclones move from the east to the west and make landfall on the eastern parts of the continent (the word “landfall” refers to the condition in which the cyclonic eye crosses the land). 

The naming process of the cyclones is a unique procedure. It makes the process of identifying different storms easier. Since 1953, Atlantic tropical storms have been named after the names listed as created by the National Hurricane System. This list is maintained and updated by an international committee of the World Meteorological Organisation. When a large-scale cyclone hit Orissa in 1999, it caused the naming of tropical cyclones that originated and developed in the North Indian Ocean. For this, the World Meteorological Organisation informed each of the eight South Asian members to submit a list of names for the cyclones in 2004. A super cyclone can be formed when a low-pressure system stays or travels for a longer time over the warm ocean surface. Also, the speed of the jet stream can influence the formation of super cyclones. 

Tornadoes and water sprouts: A tornado is a funnel-shaped, intense, small, and extremely fast-moving wind system. Its wind direction and speed of wind are mostly erratic. The wind can be as fast as 500 km per hour. The very fast blowing winds converge in the middle, and then this convergence rises up. This has the capability of plucking off trees and other weaker objects such as roof tiles of houses etc. This type of tornado is very common in the South and Western parts of the US. On the other hand, water sprouts are formed over a body of water and are similar to tornados. This can sometimes cause fish rain. 

Temperate Cyclones: Temperate cyclones form in the middle latitudes. They are formed due to the movement of air masses and fronts and are often called “dynamic cyclones” or “wave cyclones.” The stages of the formation of temperate cyclones are

Frontogenesis: This refers to the formation of air fronts by the collision of two contrasting air masses. 

Cyclone Genesis: The formation of the cyclone is due to the convergence of several fronts. 

Advancing stage: At this stage, the colder front approaches the warm front. 

Occlusion stage: In this stage, the cold front takes over from the warm front. 

Frontalysis: This is the final stage of the cyclone, when the fronts vanish and the cyclone comes to an end.

Conclusion

atmospheric disturbance is a fundamental geography concept and is important for different government exam aspirants.