Early Heat waves in India

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    • Heat waves on land and depressions in the sea this year have started early in and around India, most probably because of an unexpected climatic anomaly which could, in turn, be linked to global warming.

    What are Heat Waves?

    • Heat waves are defined as prolonged episodes of extreme temperature over any region. 
      • Apart from temperature, humidity is an important parameter considered for declaring heat-related stress.
    • 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 in the month of March to June. 
    • Factors: The possible factors responsible for Heat Waves include shifting of jet streams, El-Nino and La-Nina, anthropogenic factors like heat islands etc. 

    Criteria to Define Heat Waves

    • The Indian Meteorological Department (IMD) has provided the following criteria to define Heat Waves:
      • Heat waves need not be considered till the maximum temperature of a station reaches at least 40°C for Plains and at least 30°C for Hilly regions.
      • When  the normal maximum temperature of a station is less than or equal to 40°C, then an increase of 5°C to 6°C from the normal temperature is considered to be heat wave condition.
        • Further, an increase of 7°C or more from the normal temperature is considered a severe heat wave condition.
      • When the normal maximum temperature of a station is more than 40°C, then an increase of 4°C to 5°C from the normal temperature is considered to be heat wave condition
        • Further, an increase of 6°C or more is considered a severe heat wave condition.
      • When the actual maximum temperature remains 45°C or more irrespective of normal maximum temperature, heat waves should be declared.

    Favorable conditions for Heat Wave

    • Transportation / 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).
    • Absence of moisture in the upper atmosphere (As the presence of moisture restricts the temperature rise).
    • The sky should be practically cloudless (To allow maximum insulation over the region).
    • Large amplitude anticyclonic flow over the area.
      • Heatwaves generally develop over Northwest India and spread gradually eastwards & southwards but not westwards (since the prevailing winds during the season are westerly to north westerly). 
      • But on some occasions, heat waves may also develop over any region in situ under the favourable conditions.

    Implications of Heat Waves

    • It leads to physiological stress, which sometimes can claim human life. 
    • There are five physiological mechanisms that are triggered by heat exposure: 
      • Ischemia (reduced and restricted blood flow), 
      • heat cytotoxicity (cell death), 
      • inflammatory response (swelling), 
      • disseminated intravascular coagulation (abnormal blood clotting), and 
      • rhabdomyolysis (breakdown of muscle fibres).
    • These mechanisms affect seven vital organs: The brain, heart, intestines, kidneys, liver, lungs and pancreas. 
    • There are 27 lethal combinations of these mechanisms and organs that have been shown to be caused by heat.
    • Severe heat waves have caused catastrophic crop failures, thousands of deaths from hyperthermia, and widespread power outages due to increased use of air conditioning.
    • The signs and symptoms are as follows:
      • Heat Cramps: Ederna (swelling) and Syncope (Fainting) generally accompanied by fever below 39°C i.e.102°F.
      • Heat Exhaustion: Fatigue, weakness, dizziness, headache, nausea, vomiting, muscle cramps and sweating.
      • Heat Stroke: Body temperatures of 40°C i.e. 104°F or more along with delirium, seizures or coma. This is a potential fatal condition.
    • Exposure to heatwaves compromises the body’s ability to regulate temperature and can result in a cascade of illnesses, including heat cramps, heat exhaustion, heatstroke, and hyperthermia.
    • It affects the transmission of diseases, health service delivery, air quality, and critical social infrastructures such as energy, transport, and water.

    What is La Niña?

    • The reason behind early heat waves, early depressions and the weird dust storms is the continued persistence of a north-south low pressure pattern that forms over India during winters when a La Niña phenomenon is occurring in the equatorial Pacific Ocean.
    • The sea surface temperatures over the east and central Pacific Ocean become cooler-than-average during La Niña. This affects the trade winds flowing over the ocean surface through change in wind stress.
    • The trade winds carry this weather disturbance elsewhere and affect large parts of the world.
    • In India, the phenomenon is mostly associated with wet and cold winters. Therefore, the current effect of La Niña is completely unexpected.
    • If the interaction between the La Nina and the warm Arctic is in fact happening then it is an impact of global warming induced by human greenhouse gas emissions.

    Initiatives of weather predictions

    • Mausam App: It is a new mobile application called “Mausam” for the Indian Meteorological Department (IMD) which will help users track weather updates and also bring in the enhanced forecast as well as warning services from the government.
    • Meghdoot App: The Ministries of Earth Sciences and Agriculture have launched a mobile application that will provide location, and crop and livestock-specific weather-based agro advisories to farmers in local languages
    • Damini App: The Indian Institute of Tropical Meteorology (IITM) launched ‘Damini’, a free mobile-based application that can warn people about lightning at least 30-45 minutes before it strikes.

    Strategies to Address Heat Waves

    • Establishment of Early Warning System and Inter-Agency Coordination for prediction of heat waves and issuance of alert. 
    • Public Awareness and community outreach to increase public awareness on how to protect against extreme heat through different mediums. 
    • Capacity building and training programme for health care professionals at different levels to recognize and respond to heat wave related illnesses. 
    • Collaboration with non-government organizations (NGOs) and civil society to provide support in distress situations.
    • Encourage traditional methods of handling heat waves like wearing cotton clothes etc.
    • Reviewing labour laws and other regulations taking climatic conditions into account.
    • Improving the infrastructure setup like including shadowed windows, insulated houses etc.

    Source: DTE