A cyclone is defined as any low-pressure area with inward spiraling winds. In the northern hemisphere, cyclones rotate anticlockwise, while in the Southern Hemisphere, they rotate clockwise. Cyclogenesis is the process of cyclone formation and intensification. This article will explain to you about Cyclones in detail which will be helpful in preparing Geography for the UPSC Civil services exam.

Cyclones

• Cyclones are a type of low-pressure environment with rapid inward air circulation.
• In the Northern Hemisphere, air flows counterclockwise, while in the Southern Hemisphere, it circulates clockwise.
• Storms and poor weather are frequently associated with cyclones.
• The word Cyclone comes from the Greek word Cyclos, which means snake coils.
• Henry Paddington invented the term because tropical storms in the Bay of Bengal and the Arabian Sea resemble coiled sea serpents.

Anticyclone

• An anticyclone is just the opposite of a cyclone.
• The winds of an anticyclone swirl clockwise in the Northern Hemisphere around a high-pressure area.
• From above, air enters and sinks to the earth.
• Fairweather is usually associated with high-pressure centers.

Formation

• Cyclogenesis is an important factor in the generation and strengthening of cyclones.
• It's a catch-all term for a number of various processes that result in a cyclone.
• Tropical cyclones occur near the equator over warm ocean water.
• Warm, moist air at the ocean's surface rises upward.
• This results in a low-pressure zone close to the surface.
• This causes cooler air from the surrounding areas to flow into the low-pressure area.
• Even this frigid air is now warm and moist, and it rises.
• The cycle described above continues.
• The water in the air cools as warm wet air rises, resulting in the development of clouds.
• This cycle repeats itself, resulting in a cyclone.
• A tropical storm occurs when winds exceed 63 miles per hour, and a tropical cyclone or hurricane occurs when winds reach 119 miles per hour.

Local Names of Cyclone

In different areas, cyclones are referred to by different names.

1. Hurricanes – In the Atlantic and Eastern Pacific.
2. Typhoons – In Southeast Asia
3. Cyclone – In the Indian Ocean and Western Pacific around Australia.

Naming Process for a Cyclone

• An international committee of the World Meteorological Organisation maintains and updates cyclone lists and names (WMO).
• Only women's names were on the original lists.
• Men's names were added to the list in 1979.
• Men's and women's names are alternately used.
• Six different lists are used in a rotating fashion.
• As a result, the 2020 list will be used again in 2026.
• If the storms have inflicted damage on a country, the names will not be mentioned again for obvious reasons.
• Katrina in the United States (2005), Sandy in the United States (2012), Haiyan in the Philippines (2013), Irma, and Maria in the Caribbean are examples (2017).

Types of Cyclones

Cyclones are of two types:

1. Tropical cyclones
2. Extratropical cyclones (also called Temperate cyclones or middle-latitude cyclones or Frontal cyclones or Wave Cyclones).

1. Tropical Cyclones:

• The term 'Tropical Cyclone' is used by the World Meteorological Organization to describe weather systems with winds greater than 'Gale Force' (minimum of 63 km per hour).
• In the region between the Tropics of Capricorn and Cancer, tropical cyclones form. They're large-scale weather systems that form over tropical or subtropical oceans and coalesce into surface wind circulation.
• Tropical cyclones are strong storms that form over tropical oceans and then travel inland, wreaking havoc with violent winds, heavy rainfall, and storm surges.
• Tropical cyclones are one of the world's most destructive natural disasters.
• Tropical cyclones form over warm tropical oceans and intensify. The following are the favorable conditions for tropical storm creation and intensification:
  • A large area of the sea surface with a temperature above 27° C.
  • The Coriolis force is present.
  • The vertical wind speed varies slightly.
  • A weak low-pressure area or low-level-cyclonic circulation that already existed.
  • Above the sea level system, there is a higher divergence.

Stages of Tropical Cyclone Formation

Tropical cyclones can be classified into three stages throughout their development:

1. Formation and Initial Development Stage

• The transport of water vapor and heat from the warm ocean to the overlying air, largely through evaporation from the sea surface, is crucial to the creation and early development of a cyclonic storm.
• Convection with condensation of rising air above the ocean surface stimulates the creation of huge vertical cumulus clouds.

2. Mature Stage

• The air rises in powerful thunderstorms as a tropical storm intensifies, and it tends to spread out horizontally at the tropopause level. When air spreads out, a positive pressure is created at high elevations, speeding up the downward migration of air due to convection.
• When subsidence is induced, air warms up due to compression, resulting in a warm 'Eye' (low pressure centre). A mature tropical cyclone in the Indian Ocean has a concentric pattern of highly turbulent large cumulus thundercloud bands as its principal physical feature.

3. Modification and Decay

• As soon as its source of warm moist air begins to ebb or is abruptly cut off, a tropical cyclone begins to weaken in terms of core low pressure, internal warmth, and extremely fast speeds.
• This occurs after it reaches land or passes across chilly water.

2. Extratropical Cyclones/ Temperate Cyclones/ Frontal Depressions:

• Mid-latitude depressions, temperate cyclones, frontal depressions, and wave cyclones are all names for extratropical cyclones.
• In both hemispheres, these are active above the mid-latitudinal zone between 35° and 65° latitude.
• The movement is from west to east, and it is most noticeable during the winter months.
• Polar and tropical air masses collide and generate fronts in these latitude zones.

Formation of Extratropical Cyclones

• The Polar Front theory best explains the formation and evolution of temperate cyclones.
• According to this idea, a polar front is generated when warm-humid air masses from the tropics collide with dry-cold air masses from the poles.
• Because the cold air mass is denser and heavier, the warm air mass is pushed up.
• The contact of cold and warm air masses causes instability, resulting in a drop in pressure at the intersection, particularly in the center of the interactions.
• As a result of the reduced pressure, a void is generated.
• The surrounding air rushed in to fill the void, and a cyclone formed as a result of the earth's rotation.
• Extratropical cyclones contrast with the more violent tropical cyclones or hurricanes, which occur in generally constant temperature zones.

Cyclones in India

Tropical Cyclones

• The Bay of Bengal, the Arabian Sea, and the Indian Ocean are all hotspots for tropical cyclones.
• The Indian coastal states of Tamil Nadu, Andhra Pradesh, West Bengal, Odisha, and Gujarat were battered by tropical storms with significant wind speeds and heavy rainfall (These five states are more vulnerable to cyclone disasters than others in India).
• Because of the strong wind speeds and copious rain that accompany them, the majority of these cyclones are quite destructive.
• Cyclones are related to three elements that inflict destruction during their occurrence. These are the following:

1. Strong Winds/Squall: They cause damage to installations, residences, communications systems, trees, and other structures, resulting in death and property loss.
2. Torrential rains and inland flooding: Rain is a major issue for those who have lost their shelter as a result of the typhoon. Heavy rainfall is frequently dispersed across a considerable area, resulting in large-scale soil erosion and embankment deterioration.
3. Storm Surge: A powerful tropical cyclone causes an abnormal rise in sea level along the coast. Storm surge inundates low-lying coastal areas, killing people and cattle, eroding beaches and embankments, destroying vegetation, and reducing soil fertility.

Management of Cyclones

There are numerous structural and non-structural methods that can be used to effectively handle cyclone disasters.

1. Structural Methods: Construction of cyclone shelters, cyclone-resistant buildings, road links, culverts, bridges, canals, drains, saline embankments, surface water tanks, communication, and power transmission networks, and other structural measures are among the structural measures.
2. Non-Structural Methods: The measures such as early warning dissemination systems, coastal zone management, catastrophe risk management, and capacity building of all players are involved in this type.

Under the National Cyclone Risk Mitigation Project (NCRMP), which is being implemented with World Bank assistance, these measures are being adopted and addressed on a state-by-state basis.

Significance of Cyclones

• Cyclones carry heat and energy from the tropics to temperate latitudes.
• This feature makes them an essential component of the global atmospheric circulation system.
• Cyclones help to recharge aquifers, balance ocean temperatures and pull nutrients into the sea by increasing the flow of rivers and streams that carry garbage.

Conclusion

Though the effects of cyclones on human populations are threatening and devastating, tropical cyclones can also relieve drought conditions. Besides, cyclones are not only observed on Earth but also on planets like Mars, Jupiter, and Neptune.