Changing Landscape of Cyclone Formation

Context- A study recently published in the journal Climate and Atmospheric Science reports a sharp change in the likelihood of cyclone formation over the Arabian Sea in the late 1990s.

Key Highlights 

• Climate scientists examine whether observed changes in climate variables, such as reduced monsoon rainfall, increased extreme rainfall, droughts, heat waves and cyclones, are trends, shifts or decades. 
• These differences are important when planning resources such as water, plants and energy. 
• A new study suggests a change in the cyclogenesis potential of the Arabian Sea, which may be linked to a change in the pattern of a warm Arctic and cold Eurasia. 
• Global warming and changes in the system may also be involved.  
• To better understand climate risks and plan for adaptation, scientists must study natural variability and how global warming is changing it. 

Effect of climate change on the formation of cyclones: 

• Increased Precipitation: A warmer atmosphere can absorb more moisture, leading to increased precipitation. 
  • Increased rainfall results in  more heat being released, which ultimately encourages stronger winds within the cyclone. 
  • Recent studies have shown that hurricane rainfall increases by at least 7 percent for every degree of warming. 
• Cyclone Intensification: A warming climate is expected to increase wind speeds, leading to more storms strengthening into  Category 4 or 5 hurricanes / cyclones. 
• Rising temperatures: Both ocean and atmospheric temperatures play a key role in the formation of tropical cyclones. 
  • Cyclonic storms are powered by heat released by the evaporation of  ocean surface water and condensed as rain within the storm. 
  • In a warming climate, a warmer ocean increases evaporation, which in turn means more moisture in the atmosphere. 
• Sea level rise: Rising temperatures increase sea level rise and increase the depth of stormwater runoff. 
  • As the sea level rises, the storm reaches deeper inland. 
• Reduced Storm Speed: The speed of a cyclone can significantly affect the total amount of rain at a given location. 
  • Slower moving storms allow a longer time for precipitation to accumulate. 
  • Although research shows that the speed of the storm is slowing, the underlying mechanisms are still unclear. 
• Storm Fusion: In an increasingly warming world, the convergence of two large tropical storms over any ocean in the world can cause the formation of a massive super cyclone. 

Effects of the changing landscape of cyclones and its consequences: 

• Increased destruction: Stronger storms can cause significantly more damage to both people and the economy. 
  • Cyclone Amphan hit eastern India and Bangladesh in May 2020. 
  • In India, the storm killed 98 people and more than 5,00,000 people were evacuated from Bengal and Odisha. 
• Forecasts: The rapidly evolving nature of storms has made conventional forecasting methods unreliable. 
  • This unpredictability directly affected the ability to take adequate precautions. 
• Increasing frequency of storms: The number of hurricanes that occur each year may change in the future.  
  • However, there is no universally accepted theory that fully explains the number of storms in the current climate or predicts how it might change in the future. 
• Changing impact zones: Recent studies show that the areas where storms reach maximum intensity are gradually moving towards the Earth’s poles. 
  • This change has significant implications for the core areas of these storms. 
  • In 2021, Gujarat  faced  Cyclone Tauktae, the deadliest cyclone to hit the Arabian Sea in the last decade. 
  • According to reports, the gale force winds and rains have killed around 70 people and more than 8,000 livestock and damaged up to 88,000 homes.
  • 2,80,000 people were evacuated from  coastal areas. 
  • Climate scientists use different terms to describe observed changes in climate variables. 
  • These include; 
• Trend: a trend means that a climate variable is constantly changing in one direction, such as a steady increase in temperature.  
  • The term “human-induced trend” indicates that these changes occur during a person’s lifetime, although the exact time frame over which a variable becomes a trend is not always clear.  
• Secular trend: This term is used when a variable has increased or decreased over a long period of time. 
  • For example, a variable may have a secular trend if it has increased continuously for 30 years over a 100-year period.  
• Decadal variability: Decadal variability refers to changes from  positive phase to  negative phase  over  decades. 
  • This is somewhat similar to the concept of change, but decadent variability is often cyclical. 
• Transition: A transition represents a rapid transition from one state to another, such as a sudden change in precipitation or temperature.  
  • It can be an irreversible jump or a temporary change that later returns to its previous state.  

About cyclones: 

• The word cyclone is derived from the Greek word Cyclos, which means the coils of a snake.  
• It was coined by Henry Peddington because tropical storms in the Bay of Bengal and the Arabian Sea look like coiled sea serpents. 
• They are caused by atmospheric disturbances around an area of ​​low pressure characterized by rapid and often destructive circulation of air. 
• They are usually accompanied by violent storms and bad weather. 
• Air circulates counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. 

The way forward: 

• Therefore, a study highlighting changes in the potential for cyclone formation in the Arabian Sea in the late 1990s is a compelling example of the complex interaction between climate patterns and regional climate phenomena. 
• This highlights the importance of distinguishing between trends, changes and decay cycles in climate research and their implications for resource planning and climate adaptation.

Source: The Hindu 

Practice question:

Q. Shed light on the formation of cyclone.

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