Cyclone Dana | 24 Oct 2024

Source: DTE 

Why in News?

According to the India Meteorological Department (IMD), Cyclone Dana is expected to make landfall as a severe cyclone (wind speed: 89 to 117 kmph) along the Odisha coast near Bhitarkanika National Park and Dhamra Port. 

What are Key Facts About Cyclone Dana? 

• About: 
  • Emergence: It is the third cyclone to form in the North Indian Ocean region and the second to make landfall along the Indian coast in 2024 after Cyclone Remal.  
    • It is the first cyclone in the post monsoon cyclone season. 
  • Naming of Dana: The World Meteorological Organisation (WMO) states that Cyclone Dana was named by Qatar. In Arabic, "Dana" signifies 'generosity' and also refers to 'the most perfectly sized, valuable, and beautiful pearl.' 
• Reasons for Intense Rainfall: 
  • Intense Convection: The cyclone is showing intense convection in its western sector, which extends up to the upper layers of the atmosphere.  
    • Intense convection begins when warm, moist air rises, cools, and expands, causing moisture to condense into water droplets and form clouds.  
    • As the rising air continues to cool and condense, it forms cumulonimbus clouds, typical of thunderstorms and creates conditions conducive to heavy rainfall  
  • Warm Moist Air: There is an influx of warm, moist air into the core of the cyclone, which further enhances convection leading to more intense rainfall. 
    • The influx of warm, moist air helps to maintain and intensify the cyclone and enhances the cyclone's strength which results in intense rainfall over a relatively small area. 
  • Madden Julian Oscillation (MJO) Influence: Currently, MJO is conducive for convection hence heavy rainfall. 
    • The MJO is made up of two parts: an enhanced rainfall phase and a suppressed rainfall phase. 
      • During the enhanced phase, surface winds converge, causing air to rise and create more rainfall. In the suppressed phase, winds converge at the top of the atmosphere, causing air to sink and leading to less rainfall. 
      • This dipole structure moves west to east in the Tropics, creating more cloudiness and rainfall in the enhanced phase, and more sunshine and dryness in the suppressed phase. 

What Factors are Responsible for Formation of Tropical Cyclones? 

• Warm Ocean Waters: Sea surface temperatures of at least 27°C are essential for tropical cyclone development. Warm water provides the heat and moisture needed to fuel the storm's rising air and convection process. 
• Coriolis Force: The Coriolis effect, caused by Earth's rotation, is necessary to give the cyclone its spin. This force is weak near the equator, so tropical cyclones generally form at least 5° north or south of the equator . 
• Low Wind Shear: Low vertical wind shear (the difference in wind speed and direction at different altitudes) is crucial. High wind shear can disrupt the vertical structure of the storm, preventing it from strengthening . 
• Pre-existing Disturbance: A tropical disturbance, such as a low-pressure system, provides the initial organisation of air circulation around which a cyclone can form. 
• Convergence of Air: The convergence of warm, moist air at the surface, which rises and cools, creating clouds and thunderstorms, is fundamental to developing the cyclone's core. 

What are the Impacts of Cyclone? 

• Human Impact: Cyclones can cause widespread casualties due to strong winds, storm surges, and flooding. Thousands of people may be evacuated or displaced, leading to temporary or permanent loss of homes. 
• Infrastructure Loss: Strong winds can cause power outages and structural damage, while flooding disrupts transportation and communication. 
• Environmental Impact: High winds and storm surges erode coastlines, destroying natural habitats and human structures along the shore.  
  • Cyclones can cause long-term damage to forests, wetlands, and marine ecosystems, affecting biodiversity. 
• Agriculture Loss: Low-lying agricultural areas are vulnerable to seawater intrusion and waterlogging from heavy rains, which can destroy crops and reduce agricultural productivity. 
  • Prolonged rainfall may lead to water accumulation in fields, affecting soil health and damaging crops. 

What Measures are Needed for Effective Cyclone Disaster Preparedness and Mitigation? 

• Before Cyclone: 
  • Land Use Planning: Implement land use and building codes to restrict habitation in vulnerable zones, reserving them for parks or flood diversion. 
  • Cyclone Early Warning System: Utilise the new Impact-Based Cyclone Warning System to communicate risks and preparedness actions, focusing on local populations and land use patterns. 
  • Engineered Structures: Build structures designed to withstand cyclone winds, including public infrastructures like hospitals and communication towers. 
  • Mangrove Plantation: Promote mangrove planting initiatives to shield coastal areas from storm surges and erosion, engaging community participation in these projects. 
• During Cyclone: 
  • Cyclone Shelters: Establish cyclone shelters in high-risk areas and ensure that shelters are connected to major roads for quick evacuation and access during emergencies. 
  • Flood Management: Implement sea walls, embankments, and drainage systems to control water flow and reduce flooding from storm surges and heavy rainfall. 
• After Cyclone: 
  • Hazard Mapping: Create maps that indicate the frequency and intensity of cyclones based on historical data, including storm surges and flooding risks. 
  • Retrofitting Non-Engineered Structures: Educate communities on retrofitting techniques, such as building steep-slope roofs and anchoring poles, to enhance the resilience of non-engineered homes. 

Conclusion 

Cyclone Dana underscores the importance of proactive disaster management measures, including effective early warning systems, land use planning, and community involvement. By enhancing infrastructure resilience, implementing hazard mapping, and promoting mangrove conservation, we can better prepare for and mitigate the impacts of cyclones on vulnerable coastal regions.