Current Affairs

Important Geophysical Phenomena

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  • Published
    3rd Feb, 2021
  • Context

    High-intensity tropical cyclones have been moving closer to coasts over the past 40 years, potentially causing more destruction than before, as per a study. The research is published in Science.

  • Background

    • The team analysed global data from 1982-2018 on tropical cyclone formation, movement and intensity mainly gathered from satellite observations.
    • In the observation, it has been found that at maximum intensity, cyclones were on average getting 30km closer to coastlines per decade.
    • There were also on average two more cyclones per decade within 200 km of land.
    • The study emphasis on the need to understand all aspects of tropical cyclones.
  • Analysis

    Understanding the geography of Hurricances

    • Hurricanes are large, swirling storms with winds of 119 kilometers per hour (74 mph) or higher.
      • That's faster than a cheetah, the fastest animal on land.
    • The storms form over warm ocean waters and sometimes strike land.
    • When a hurricane reaches land, it pushes a wall of ocean water ashore. This wall of water is called a storm surge, which along with heavy rain can cause flooding, especially near the coast.

    The different terms hurricanes, typhoons and tropical cyclones all refer to tropical storms. They are named differently depending on the region they occur in.

    • Hurricanes are tropical storms that form over the North Atlantic Ocean and Northeast Pacific.
    • Cyclones are formed over the South Pacific and Indian Ocean.
    • Typhoons are formed over the Northwest Pacific Ocean
  • How hurricanes are categorized?

    • Hurricanes are categorized according to the speed of their maximum sustained winds.
    • The scale used for this purpose, called the Saffir-Simpson Hurricane Wind Scale, was developed in 1971 by civil engineer Herbert Saffir and by meteorologist and then-director of the U.S. National Hurricane Center, Bob Simpson.
    • The Saffir-Simpson scale rates a hurricane's severity from 1 (very dangerous) to 5 (catastrophic), based on the following wind speeds: 
      • Category 1: Winds of 74-95 mph (119-153 km/h)
      • Category 2: Winds of 96-110 mph (154-177 km/h)
      • Category 3: Winds of 111-129 mph (178-208 km/h)
      • Category 4: Winds of 130-156 mph (209-251 km/h)
      • Category 5: Winds exceeding 157 mph (252 km/h)
  • Key-highlights of the Study

    • Previously, studies have shown that the maximum intensity of tropical cyclones is found further towards the poles. However, this does not necessarily mean these more poleward storms are more devastating.
    • Western ward shift: The new findings show cyclones at maximum intensity are also migrating westward, bringing them closer to coastlines and increasing their potential for damage.
    • Occurrence of additional cyclone: Each decade since the 1980s, an additional two cyclones have come within 124 miles (200 km) of land.
  • Reasons behind the shift

    • The exact mechanism for this enhanced westward steering is unknown, but it may be due to the same underlying mechanism for poleward migration of cyclones as rising temperatures cause atmospheric patterns to shift.
    • The researchers also stated that it could be connected to changes in tropical atmospheric patterns possibly caused by climate change.
  • Atlantic Zone, a special case?

    • Cyclones across the globe are moving closer to land, except Atlantic hurricanes.
    • It's mysterious that, unlike other areas, the Atlantic hurricane basin didn’t show any significant westward shift.
    • The reason is not sure but that could be because the Atlantic hurricane zone is more closely surrounded by continents.
    • The busiest tropical cyclone basin is in the western Pacific, where there are the most landfalls and the shift westward is twice as big as the global average.
  • A puzzling situation

    • Though storms are getting closer to land, researchers still have not seen a significant increase in landfalls, which “is still a puzzle”.
    • It is not only the landfall that causes damage. When the cyclone is close enough to land it can also cause damage like Hurricane Sandy and Dorian in 2019, both of which skirted along the US coast for a considerable time before making landfall.
  • Are Hurricanes impacted by climate change?

    • Hurricanes feed off of heat energy, so as Earth's global temperatures continue to rise, hurricanes are bound to be affected.
    • So far, it's not evident that hurricanes are necessarily forming more often because of rising temperatures, although scientists do predict that hurricane activity and intensity will likely increase in future years. 
  • How does it impact?

    • Impact on economy: Globally, 80 to 100 cyclones develop over tropical oceans each year, impacting regions in the Pacific, Atlantic and Indian Oceans and causing billions of dollars of damage.
    • Risk to coastal communities: These storms are likely becoming more destructive as they spend more time along coastlines at their highest intensities. The risk to some coastal communities around the world may be increasing and that will have profound implications over the coming decades.
    • Other impacts are:
      • Impact on environment: Destruction to flora and fauna
      • Agricultural loss
      • Loss of life and livelihood
  • Conclusion

    This new research is plausible, especially since scientists have already seen a shift of storms more toward the north and south poles, but it raises questions that require follow up, especially why no corresponding increase in landfalls has been found. All these strange shifts are taking cyclones out of their preferred environment of warm tropical waters away from land.

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