Date: 27/09/2022

Relevance: GS-3: Environmental hazard and Disaster

Key Phrases: Saffir-Simpson Scale, Cyclones, Typhoons, And Hurricanes, Shifting In The Season Of Hurricanes, Shift In Landfall Pattern

Why in News?

• Hurricane Fiona hit the Atlantic coasts of Puerto Rico and the Dominican Republic, causing widespread damage and leaving more than 1 million people without running water or power.

What is a hurricane?

• Hurricanes are low-pressure systems with organized thunderstorm activity that forms over tropical or subtropical waters.
• In a hurricane, spiraling winds draw moist air toward the center, fueling the towering thunderstorms that surround it.
• They form over the tropics, where they have an abundant source of heat to maintain their strength for days at a time.

How hurricanes are formed?

• As the air gets warm due to climate change, hurricanes can hold more water vapor, producing more intense rainfall rates in a storm.
• These rotating winds lead to the development of the characteristic “eye” of the hurricane, the calm, clear center of the storm.
• The eye is surrounded by the eyewall, where winds are strongest.
• Hurricanes draw their strength from warm ocean waters.
• In the North Atlantic, even as these storms veer away from the tropics, they then encounter the very warm waters of the Gulf Stream.
• This can either sustain them or even cause them to re-intensify as they make their way up the east coast of the United States towards Canada.
• As storm systems strengthen into hurricanes, the surface winds move continuously in a circular motion. Meteorologists refer to this pattern as “closed circulation."
• The direction of circulation is different depending on where the storm is located: it is counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Conditions needed for the formation of the hurricane:

• warm ocean water
• lots of moisture in the air
• low vertical wind shear
• a pre-existing disturbance (e.g., a cluster of thunderstorms)

How are hurricanes measured?

• The Saffir-Simpson scale is the scale used to rate hurricanes which is based on the wind speeds.
• The scale rates hurricanes on a scale of 1 to 5 based on the hurricane’s sustained wind speed.

What is the difference between cyclones, typhoons, and hurricanes?

• These big storms get different names depending on where and how they were formed.
• Storms that form over the Atlantic Ocean or central and eastern North Pacific are called "hurricanes" when their wind speeds reach at least 74 miles per hour (119 kilometers per hour). Up to that point, they're known as "tropical storms."
• In East Asia, violent, swirling storms that form over the Northwest Pacific are called "typhoons", while "cyclones" emerge over the Indian Ocean and South Pacific Ocean.

How is climate change affecting hurricanes?

• The intensity of tropical cyclones has increased globally in recent decades, with the proportion of Category 3 to 5 cyclones growing by around 5 percent per decade since 1979.
• The climate change is making hurricanes wetter, windier, and more intense.
• There is evidence that climate change is causing storms to travel slower, capable of dumping more water in one place.
• During the 2020 Atlantic hurricane season, climate change boosted hourly rainfall rates in hurricane-force storms by 8-11 percent.
• The world has already warmed 1.1 degrees Celsius above the pre-industrial average.
• Scientists at the US National Oceanic and Atmospheric Administration (NOAA) expect that, at 2C of warming, hurricane wind speeds could increase by up to 10 percent.
• NOAA also projects that the proportion of hurricanes reaching the most intense levels with Category 4 or 5 could rise by about 10 percent this century.

How else is climate change affecting storms?

• Shifting in the season of hurricanes:
  • Climate warming is creating conditions conducive to storms in more months of the year shifting the typical "season" for hurricanes.
• Shift in landfall pattern:
  • Hurricanes are making landfall in regions far outside the historic norm.
  • According to NOAA, in the US, Florida has witnessed the most hurricanes making landfall, with more than 120 direct hits since 1851.
  • But in recent years, some storms are reaching peak intensity and making landfall farther north than in the past and a poleward shift may be related to rising global air and ocean temperatures.
  • This trend is worrying for mid-latitude cities such as New York, Boston, Beijing, and Tokyo, where "infrastructure is not prepared" for such storms.
• Early formation of storms:
  • Hurricane activity is common in North America from June through November, peaking in September after a summer buildup of warm water conditions.
  • However, the landfall in the US occurs more than three weeks earlier than it did in 1900, nudging the start of the season into May.
  • The same trend appears to be emerging across the world in Asia's Bay of Bengal, where cyclones have been forming earlier than usual in April and May ahead of the summer monsoon since 2013.
• Rise in the frequency of storms:
  • A team of scientists has recently detected a rise in the frequency of North Atlantic hurricanes over the last 150 years.

Conclusion:

• In the last 40 years, the ocean has absorbed about 90 percent of the warming caused by heat-trapping greenhouse gas emissions and much of this ocean heat is contained near the water's surface.
• This additional heat can fuel a storm's intensity and power stronger winds.
• Climate change can also boost the amount of rainfall delivered by a storm because a warmer atmosphere holds more moisture forming water vapour until clouds break, sending down heavy rain.
• Therefore, it is of utmost importance for the countries to bring all nations into a common cause to undertake ambitious efforts to combat climate change and adapt to its effects and achieve a climate-neutral world.

Source: Indian Express

Mains Question:

Q. What is a hurricane? How are they formed? Discuss the impact of climate change on hurricanes. (250 words).