Heatwaves in India- UPSC Current Affairs

Why in the News?

As per the India Meteorological Department (IMD) estimates, the month of April 2022 was the hottest in northwest India in 122 years. 

Probable Question

Examine the anthropogenic causes responsible for the rise in the frequency of heatwaves in India. 

Image Source: NASA

Key Points

How are Heat Waves defined?

• A Heat Wave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India.
• A heatwave is declared when the maximum temperature is over 40 degrees Celsius and at least 4.5 notches above normal. 
• A severe heatwave is declared if the departure from normal temperature is more than 6.4 degrees or if the maximum temperature crosses 47 degrees, according to the IMD. 
• Further, based on absolute recorded temperatures, a heatwave is declared when an area logs a maximum temperature of 45 degrees Celsius. 
• The IMD Qualitatively classifies a heatwave as one when the air temperature becomes fatal to the human body when exposed.
  • Quantitatively, it is defined based on temperature thresholds over a region in terms of actual temperature or its departure from normal.
• Heatwaves generally occur over plains of northwest India, Central, East and north Peninsular India.

Favourable conditions for Heatwave

• Prevalence of hot dry air over a region: There should be a region of warm dry air and an appropriate flow pattern for transporting hot air over the region).
• Moisture: Absence of moisture in the upper atmosphere.
• Cloudless Sky: The sky should be practically cloudless which allows maximum insulation over the region.
• Anticyclonic flow: Large amplitude anticyclonic flow over the area.

Mechanism: Formation of Heat Waves

• Heatwaves begin when high pressure in the atmosphere moves in and pushes warm air toward the ground. 
• That air warms up further as it is compressed, and we begin to feel a lot hotter.
• The high-pressure system pressing down on the ground expands vertically, forcing other weather systems to change course. 
• It even minimises wind and cloud cover, making the air more stifling.
• Heatwaves are especially common in areas that are already arid, like the desert Southwest, and at high altitudes where high-pressure systems readily form. 

Also Read: Causes behind Sinking Uttarakhand’s Town ‘Joshimath’

Causes of Heat Waves

• Lack of Rainfall: Usually, periods of high temperature are punctuated by periodic episodes of rain, but this was largely absent during March and April.
• Western Disturbances: The rain-bearing Western Disturbances, or tropical storms which bring rain from the Mediterranean over north India in March-April have been absent.
  • The rain-bearing western disturbances originate because of temperature gradients between the northernmost parts of the globe and the latitudes passing through West Asia. 
  • Weaker gradients mean weaker rains. 
• La Nina: Cool temperatures in the Central Pacific, or La Nina, that normally helps rain in India too have failed to bolster rainfall.
• Climate Change: Climate change caused by greenhouse gases from burning fossil fuels is poised to make heat waves longer, more intense, and more frequent. 
• Dry & Hot Westerly Winds: The continuous dry and hot westerly winds blowing from Baluchistan, central Pakistan and the Thar Desert over northwest and central India have contributed to the rise in heatwaves.

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Impact of Heat Waves

• The effects of the heatwave include heat-related illnesses, poor air quality, little rainfall, and reduced crop yields. 
• Additionally, Power demand has spiked, and coal inventories have dropped, leaving the country with its worst electricity shortage in more than six years. 
• In the northern regions of Uttarakhand and Himachal Pradesh, mountain snow has been rapidly melting besides raging forest fires.
• The extreme temperatures and resultant atmospheric conditions adversely affect people living in heat-prone regions causing physiological stress, sometimes resulting in death.
• Heat conditions can alter human behaviour, the transmission of diseases, health service delivery, air quality, and critical social infrastructures such as energy, transport, and water.

Strategy to Deal with Heatwaves

• In 2016, the NDMA drew up the first national guidelines for heatwaves titled 'Preparation of Action Plan–Prevention and Management of Heat Wave'.
• The National Guidelines on Heat Wave mentions the roles and responsibilities of the central and state government agencies, district administrations, local self-governments, NGOs, civil society organisations and other stakeholders in a matrix format.

Heat Action Plan

• Since 2013, the India Meteorological Department (IMD), in collaboration with local health departments, has started issuing heat action plans in many parts of the country to forewarn about heatwaves as well as advise action to be taken during such occasions.
• India Meteorological Department issues the following colour code impact based heat warning jointly with National Disaster Management Authority:

Image Source: India Meteorological Department

Way Forward

• A Multipronged approach is needed to tackle heat waves which could include:

• First, public awareness and community outreach to share information on the risks of heatwaves and dos and don'ts to prevent heat-related deaths and illnesses. 
• Second, an early warning system in place to alert citizens about the onset of the heatwave and set inter-agency coordination in motion. 
• Third, to build capacity among healthcare professionals, including paramedical staff and community health staff. 
• Cities must adopt a range of actions related to urban planning and governance, and governmental and community preparedness. 

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