heat-wave-sweeps-north-india

Context: Several parts of north India reeled under an intense heatwave with many districts in Rajasthan, Haryana, Uttar Pradesh, Madhya Pradesh posting temperatures over 45 degrees Celsius or five degrees above what is normal.

More on News:

  • Churu in Rajasthan registered 47° C whereas Prayagraj in Uttar Pradesh recorded 46° C. 
  • The India Meteorological Department had forecast “heatwave to severe heatwave conditions” over northwest, central and adjoining peninsular India for most of the week along with heavy rain over northeast India.
  • Rising temperature: Many parts of coastal Andhra Pradesh, Odisha and Maharashtra also saw temperatures soar above 42° C, triggering heatwave conditions.
    • The heat was due to dry northwesterly winds prevailing over northwest and central India. 

Current scenario: 

  • The State and district administrations have warned the residents to take precautions against the heat waves.
  • The IMD said that summer temperatures in May — on average — were lower than usual mostly due to several rain-bearing Western Disturbances.
  • High summer temperatures in north India are one of the factors important for drawing in the monsoon rain into Kerala, however, cyclone Amphan might delay this advent. 
  • The IMD had said that it expected the monsoon to hit Kerala only on June 5, while Skymet, a private weather forecast agency, disagreed saying it might hit the State by May 28. 
  • Beginning Saturday (23rd May), temperatures are finally in the realm of normal for this time of the year in north India .

Measures to Deal with it:

  • Sensitizing States to the need of preparing and implementing specific Heat Action Plans in line with NDMA’s national guidelines on Heat Wave.
  • Establish Early Warning System and Inter-Agency Coordination to alert residents on predicted high and extreme temperatures.
  • Capacity building/training program for health care professionals at the local level to recognize and respond to heat-related illnesses, particularly during extreme heat events.
  • Public Awareness and community outreach: Disseminating public awareness messages on how to protect against the extreme heat-wave through print, electronic and social media and Information, Education and Communication (IEC) materials.
  • Collaboration with non government and civil society in building temporary shelters, wherever necessary, improved water delivery systems in public areas and other innovative measures to tackle Heat wave conditions.
  • Knowledge of effective prevention and first-aid treatment, besides awareness of potential side-effects of prescription drugs during hot weather, is crucial for physicians and pharmacists.
  • Sharing experiences and best practices to help other stakeholders prepare and implement their Heat Action Plans.

Heat Wave:

  • The heatwave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the pre-monsoon (April to June) summer season. 
  • Heat waves typically occur between March to June, and in some rare cases even extend till July. 
  • The heatwave is considered if the maximum temperature of a station reaches at least 40°C or more for Plains, 37°C or more for coastal stations and at least 30°C or more for Hilly regions. Following criteria are used to declare heat wave:

a) Based on Departure from Normal

Heat Wave: Departure from normal is 4.5°C to 6.4°C

Severe Heat Wave: Departure from normal is >6.4°C

b) Based on Actual Maximum Temperature (for plains only)

Heat Wave: When actual maximum temperature ≥ 45°C

Severe Heat Wave: When actual maximum temperature ≥47°C

  • To declare a heat wave, the above criteria should be met at least in 2 stations in a Meteorological subdivision for at least two consecutive days.

Formation:

  • Heat waves can form in many ways. They often form when high pressure aloft strengthens and remains over a region for several days up to several weeks.
  • This is common in summer (in both Northern and Southern Hemispheres) as the jet stream 'follows the sun'. 
  • On the equator side of the jet stream, in the middle layers of the atmosphere, is the high-pressure area.
  • Summertime weather patterns are generally slower to change than in winter. As a result, this mid-level high pressure also moves slowly.
  • Under high pressure, the air subsides (sinks) toward the surface. This sinking air acts as a dome capping the atmosphere. This cap helps to trap heat instead of allowing it to lift.
  • Without the lift, there is little or no convection and therefore little or no convective clouds (cumulus clouds) with minimal chance for rain. The lack of clouds means that an affected area is struck with strong sunlight.
  • The end result is a continual build-up of heat at the surface that we experience as a heat wave.

Impact:

  • Health hazards - According to the National Health Service based in the UK, heat stroke and heat exhaustion are the two major risks posed by high-temperature conditions.
    • Continuous and constant exposure to high temperatures could result in nausea and heat cramps, resulting in a rapid rise of the body temperature.
    • Dehydration (absence of adequate water within the body) could also aid in heat exhaustion.
  • Adverse Effects On Mental Health - Research has revealed that exposure to high temperatures over a sustained period of time can have a negative impact on the psychology of a person.
    • It has also been observed that crime rates go up when the temperature rises.
    • Also, higher temperatures lead to lesser income as people are unable to devote sufficient time to work due to the heat-associated stress.
  • Infrastructural Damage - As heat causes the metal to expand, heat waves can lead to major infrastructural defects.
    • Power transformers can detonate causing fires.
    • Water lines can burst to cause the loss of water and water shortage.
    • Heat waves can also induce the kinking or buckling of railroads.
    • Highways can melt or develop cracks in extreme heat. For example, two traffic lanes in Oklahoma City, US, had to be closed during the 2006 North American heat wave after they buckled under the heat.
  • Trigger Devastating Wildfires - When a heat wave is accompanied by an episode of drought that dries out the vegetation, it creates the ideal environment for the break-out of a wildfire or a bushfire.
  • Power Outages - The sudden spike in electricity consumption challenges the available electricity supplies of the area.

 

India Meteorological Department:

  • It is an agency of the Ministry of Earth Sciences of the Government of India. 
  • It is the principal agency responsible for meteorological observations, weather forecasting and seismology.
  • It was formed in 1875. 
  • IMD is headquartered in Delhi and operates hundreds of observation stations across India and Antarctica. 
  • Regional offices are at Mumbai, Kolkata, Nagpur and Pune.
  • IMD is also one of the six Regional Specialised Meteorological Centres of the World Meteorological Organization. 
  • It has the responsibility for forecasting, naming and distribution of warnings for tropical cyclones in the Northern Indian Ocean region, including the Malacca Straits, the Bay of Bengal, the Arabian Sea and the Persian Gulf

 

Western Disturbances:

  • A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.
  • It is a non-monsoonal precipitation pattern driven by the westerlies
  • The moisture in these storms usually originates over the Mediterranean Sea and the Indian Ocean.
  • Extratropical storms are a global phenomenon with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere. 
  • In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas. 
  • They are more frequent and strong in the winter season.
  • They are important for the development of the rabi crop, which includes the locally important staple wheat.

Source:

https://www.thehindu.com/news/national/other-states/heatwave-sweeps-north-india/article31674229.ece

Image Source: The Hindu