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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