Prelims level : Climatology Mains level : Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc., geographical features and their location - changes in critical geographical features (Including Waterbodies and Ice-Caps) And In Flora And Fauna
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Why in News:

  •    The India Meteorological Department (IMD) said severe heat wave conditions will continue in many parts, especially in Rajasthan and several parts of north and central India, In worst-hit Rajasthan, while Churu recorded the highest temperature of 48.4°C.


  •    In worst-hit Rajasthan, a farmer died of heatstroke in Sikar district, while Churu recorded the highest temperature of 48.4°C.

India Meteorological Department (IMD)

  •    The IMD is the national meteorological service of the country and it is the chief government agency dealing in everything related to meteorology, seismology and associated subjects.
  •    It was formed in 1875.
  •    The IMD is under the Ministry of Earth Sciences, Government of India

IMD Mandate:

  •    Taking meteorological observations and providing current information and forecasting information for the most favorable operation of weather-dependent activities such as irrigation, agriculture, aviation, shipping, offshore oil exploration and so on.
  •    Offering warning against severe weather phenomenon such as tropical cyclones, dust storms, norwesters, heat waves, cold waves, heavy rains, heavy snow, etc.
  •    Providing met-related statistics needed for agriculture, industries, water resources management, oil exploration, and any other strategically important activities for the country. Engaging in research in meteorology and allied subjects.

Heat Wave:

  •    Heat wave is considered if 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:

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.

Based on Actual Maximum Temperature (for plains only):

  1. Heat Wave: When actual maximum temperature ≥ 45°C
  2. Severe Heat Wave: When actual maximum temperature ≥47°C
  •    To declare heat wave, the above criteria should be met at least in 2 stations in a Meteorological sub-division for at least two consecutive days and it will be declared on the second day.
  •    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. Heat Waves typically occur between March and June, and in some rare cases even extend till July. The extreme temperatures and resultant atmospheric conditions adversely affect people living in these regions as they cause physiological stress, sometimes resulting in death.
  •    Detection and location of earthquakes and evaluation of seismicity in various parts of the country for developmental projects.

How do heat waves affect us?

  •    The health impacts of Heat Waves typically involve dehydration, heat cramps, heat exhaustion and/or heat stroke. 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 Stoke: Body temperatures of 40*C i.e. 104*F or more along with delirium, seizures or coma. This is a potential fatal condition.
  •    Heat waves killed 1,422 in Andhra Pradesh and 541 in Telangana in 2015 or about 90% of all the heat wave mortality of that year.
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