Cyclone

Mains Marks Booster     5th August 2023        
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Introduction

A cyclone is a large, rotating storm system with low pressure at its center. Cyclones can form in any ocean basin, but they are most common in the tropics. Cyclones can cause a variety of hazards, including strong winds, storm surges, and heavy rainfall.

Types of cyclones

  • Tropical cyclones: These are the most common type of cyclone. They form over warm, tropical oceans and are characterized by strong winds, heavy rainfall, and storm surges.
  • Extratropical cyclones: These cyclones form over cooler waters and are not as strong as tropical cyclones. They are characterized by strong winds, heavy rainfall, and snow.
  • Midlatitude cyclones: These cyclones form in the midlatitudes and are characterized by strong winds, heavy rainfall, and snow.

Causes of Cyclones

  • Warm Ocean Waters: Cyclones form over warm tropical or subtropical ocean waters with a sea surface temperature exceeding 26.5°C (80°F), providing energy and moisture for their formation and intensification.
  • Coriolis Effect: Earth's rotation causes the Coriolis effect, deflecting air as it moves from high to low pressure. In the Northern Hemisphere, it causes a counterclockwise rotation in cyclones, while in the Southern Hemisphere, it leads to a clockwise rotation.
  • Low Vertical Wind Shear: Cyclones require low vertical wind shear, which is a minimal change in wind speed and direction with height. 
  • This enables the storm system to maintain its structure and promotes the organization of thunderstorms around the center. High wind shear disrupts cyclone development and intensification.
  • Moisture and Instability: Cyclones thrive in environments with abundant moisture and atmospheric instability. The rise of warm, moist air creates convection currents and thunderstorms. 
      • As the air rises, it cools and condenses, releasing latent heat that further fuels cyclone energy and intensification.
  • Atmospheric Convergence: Cyclones form where air masses with different properties, such as temperature and humidity, converge, causing atmospheric convergence. 
      • This convergence leads to the upward movement of air and the development of a low-pressure center, which is essential for cyclone formation.
  • Tropical Disturbances: Cyclones often originate from tropical disturbances, which are areas of organized thunderstorms with weak pressure gradients. Under favorable conditions, these disturbances can evolve into tropical depressions, storms, and eventually cyclones.
  • Seasonal Variations: Cyclone formation is influenced by seasonal variations. Specific times of the year, known as the hurricane or cyclone season, are characterized by favorable oceanic and atmospheric conditions for cyclone development. 
    • This season typically occurs in regions such as the Atlantic Ocean, the Caribbean Sea, and the eastern Pacific Ocean.

Formation of Cyclones

  • Warm ocean temperatures: Cyclones thrive on warm waters with temperatures above 26.5°C (80°F) as they serve as a primary source of energy for their formation and intensification.
  • Favorable atmospheric conditions: The presence of a pre-existing weather disturbance, such as a tropical wave or low-pressure system, can provide the initial trigger for cyclone development. Additionally, low vertical wind shear is crucial for cyclone formation and maintenance.
  • Moisture and instability: Sufficient moisture in the lower atmosphere and unstable atmospheric conditions contribute to the development of thunderstorms, which are the building blocks of a cyclone.

As a cyclone develops, it undergoes different stages, including tropical depression, tropical storm, and eventually reaching hurricane/typhoon/cyclone intensity. The warm ocean waters provide the energy needed for the cyclone to strengthen, and the rotation of the Earth causes the system to spin and develop a distinct eye at its center.

cyclone

Impact of Cyclones

Cyclones can have significant impacts on the areas they affect:

  • Strong winds: Cyclones are characterized by powerful winds that can cause extensive damage to buildings, infrastructure, and vegetation. 
  • These winds can reach speeds exceeding 119 kilometers per hour (74 mph) in tropical storms and much higher in severe hurricanes/typhoons/cyclones.
  • Heavy rainfall and flooding: Cyclones bring intense rainfall, which can lead to flash floods and river flooding. The heavy precipitation can cause landslides, damage crops, and disrupt water and sanitation systems, increasing the risk of waterborne diseases.
  • Storm surge: It is a coastal flood or rise in sea level caused by the strong winds and low atmospheric pressure of a cyclone. It can inundate coastal areas, erode shorelines, and result in significant damage and loss of life.
  • Tornadoes and water spouts: Cyclones can also spawn tornadoes or water spouts, which are rapidly rotating columns of air. These tornadoes can cause additional localized destruction.

Recent Cyclones: 

  • Cyclone Biparjoy, which had been brewing over the Arabian Sea for several days, made landfall in Gujarat's coastal area in June 2023. 
  • Super Cyclonic Storm Amphan (2020) - Hit parts of India and Bangladesh, causing significant damage, displacement, and loss of life.   
  • Cyclone Idai (2019) - Impacted Mozambique, Zimbabwe, and Malawi, causing severe flooding, destruction, and loss of life.  
  • Super Cyclonic Storm Amphan (2020) - Hit parts of India and Bangladesh, causing significant damage, displacement, and loss of life.

Safety Measures for Cyclones

  1. Early warning systems: Meteorological agencies monitor and track cyclones using satellites, weather radar, and other tools. Timely warnings and alerts are crucial for providing advance notice to people in the affected areas.
  2. Evacuation plans: Local authorities develop evacuation plans to relocate residents from high-risk areas to safer locations. This includes identifying evacuation routes, establishing shelters, and organizing transportation.
  3. Infrastructure preparedness: Constructing buildings and infrastructure that are designed to withstand cyclonic winds and storm surge can help minimize damage. Strengthening roofs, windows, and doors, and ensuring proper drainage systems can also be effective.
  4. Community awareness and education: Educating communities about cyclones, their impacts, and necessary safety measures can help people understand the risks and take appropriate actions. This includes teaching individuals how to secure their property, stock essential supplies, and develop personal emergency plans.
  5. Relief and recovery operations: Adequate preparations should be made for post-cyclone relief and recovery operations, including providing medical assistance, restoring essential services, and facilitating the distribution of food, water, and other necessities.

It's important to note that cyclones are natural disasters that require careful monitoring, preparedness, and coordinated responses from governments, communities, and individuals to minimize the potential damage and ensure the safety of those in their path.

Climate change is predicted to increase the frequency and intensity of extreme weather events, including cyclones. Therefore, continuous investment in research and development, capacity building, climate-resilient infrastructure, and proactive policy-making is essential for India to navigate towards resilience against the growing threat of cyclones. Emphasizing a multidisciplinary and holistic approach encompassing technology, environmental management, and community engagement is critical to combat the cyclone menace and safeguard the lives and livelihoods of millions of Indians.

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