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COLD WAVE

28th December, 2022

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Context

  • Cold wave conditions will continue in North India -India Meteorological Department.

What is a cold wave?

  • The IMD defines a cold wave qualitatively as “a condition of air temperature which becomes fatal to the human body when exposed.”
  • The IMD records a cold wave when
  1. the minimum temperature is equal to or less than 10 degree Celsius at a weather station in the plains,
  2. and the min temperature is 4.5 degrees to 6.4 degrees below the normal temperature for that period.
  • A cold wave may also be recorded at a station in the plains when the minimum temperature is less than or equal to 4 degree Celsius.
  • For hilly regions, a cold wave is declared when the minimum temperature is less than or equal to 0 degree Celsius and the minimum temperature is 4.5 degrees to 6.4 degrees below the normal.
  • The ‘normal’ temperature is calculated for every five days by taking the average temperature for these days over the past 30 years.

Cause of this cold wave

  • Cold waves usually occur from mid-December to the end of February.
  • According to the IMD, the factors that bring cold waves to India include the movement of cold air masses brought about by upper-level winds.
  • They can be triggered by strong westerly winds approaching northwest India and transporting cold air towards the southeast direction.
  • Build up of an extended area of relatively high pressure over northwest Asia can also bring cold waves.

Western Disturbance and cold wave

  • A western disturbance as a cyclonic circulation lies over north Pakistan and adjoining Jammu and Kashmir.
  • Western disturbances are storms that originate in the Mediterranean region and bring winter rainfall to northwest India.
  • After this western disturbance moves, there is a brief gap.  In this gap of five to six days, the IMD expects strong northwesterly and westerly cold winds over north India.

https://newsonair.com/2022/12/27/cold-wave-persists-in-north-west-india-cripples-normal-life-no-relief-from-biting-cold-till-thursday-says-met-dept/