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Heatwaves UPSC NOTE

 Why in news

  • Concurrent occurrences of heatwaves and extreme short-term sea level rise at the same coastal.

  • Locations significantly increased between 1998 and 2017 when compared to the preceding twenty years.

  • As per a study published in the journal Communications Earth & Environment.

  • The study also suggests that these events may be five times more likely to occur between 2025 and 2049 under a modelled high emissions scenario.

  • A so-called ‘concurrent heatwave and extreme sea level’ (CHWESL) event is when a heatwave and an extreme short-term sea level rise occur at the same coastal location over the same time period.

What is heatwaves?

  • A heatwave is a stretch of abnormally hot weather that lasts for several days.

  • Sometimes even weeks

  • Temperature: The key factor is temperatures exceeding the usual climate for a particular area

  • Duration: Heatwaves typically last for at least two or more days.

  • Humidity: High humidity often accompanies heatwaves, making it feel even hotter and increasing health risks.

  • Impact: Heatwaves can be dangerous and have severe health consequences, especially for vulnerable populations like elderly, young children, and people with chronic illnesses.

  • Risks: Heat exhaustion, heatstroke, and dehydration are some of the health risks associated with heatwaves.

  • Climate Change: Heatwaves are becoming more frequent and intense due to climate change.

Criteria for Declaring Heat Wave in India

  • The India Meteorological Department has specific criteria for declaring a heatwave in different regions of the country. 

Here's a breakdown:

  • Baseline Temperature:

    • Plains: Minimum temperature of 40°C or more is considered the base for heatwave declaration.

    • Hilly regions: A minimum temperature of 30°C or more is considered the base.

  • Departure from Normal Temperature:

    • If the normal maximum temperature of a station is less than or equal to 40°C,

      • An increase of 5°C to 6°C from normal is considered a heatwave.

      • An increase of 7°C or more from normal is considered a severe heatwave.

      • If the normal maximum temperature of a station is more than 40°C, then:

      • An increase of 4°C to 5°C from normal is considered a heatwave.

      • An increase of 6°C or more is considered a severe heatwave.

  • Absolute Threshold:

    • Regardless of the normal temperature, if the actual maximum temperature remains 45°C or more for consecutive days, a heatwave is declared.

  • Spatial Coverage:

    • The heatwave declaration applies if the above criteria are met at least in two stations within a meteorological subdivision for at least two consecutive days. 

    • The heatwave is officially declared on the second day.

  • Coastal Stations:

    • For coastal stations, a heatwave might be declared if the maximum temperature departure is 4.5°C or more from normal, provided the actual maximum temperature is 37°C or more.

Concurrent heatwave and extreme sea level

  • A concurrent heatwave and extreme sea level (CHWESL) event.

  • Its a dangerous situation that occurs when two extreme weather events happen at the same time in a coastal location. 

  • Combined Events: A CHWESL combines a heatwave with an extreme sea level rise.

  • Heatwave: This refers to a prolonged period of abnormally hot weather, exceeding the usual temperatures for that area.

  • Extreme Sea Level Rise: This is a significant rise in sea level above the predicted or normal tidal levels.



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Learnerz IAS | Concept oriented UPSC Classes in Malayalam: Heatwaves UPSC NOTE
Heatwaves UPSC NOTE
Learnerz IAS | Concept oriented UPSC Classes in Malayalam
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