Q. Which of the following is definition of a ‘cold day’ as per India Meteorological Department (IMD)?

[A] A day when maximum temperature is at least 6.5u00b0C below normal.

[B] A day when the minimum temperature is at least 6.5u00b0C above normal.

[C] A day when the maximum temperature during the day is at least 4.5u00b0C above normal.

[D] A day when the maximum temperature during the day is at least 4.5u00b0C below normal.

Answer: D
Notes:

Explanation:

  • 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.
  • Cold Day: A cold-day condition is said to prevail when the maximum temperature during the day is at least 4.5°C below normal.
  • Severe Cold Day: If the maximum temperature is at least 6.5°C below normal, it is classified as a severe cold day.
  • Cold wave: Cold wave is characterized by a rapid and marked fall of temperature. The term ‘cold’ describes an unusual fall in temperature that is triggered by the transport of cold air masses into a specific area.
  • The “wave” in cold wave is apparent in the upper-air flow (the jetstream), which is usually amplified into a strong ridge-trough pattern during a major cold outbreak. Cold waves affect much larger areas than blizzards, ice storms, and other winter hazards.

Source: https://economictimes.indiatimes.com/news/india/cold-day-cold-wave-conditions-to-grip-northwest-india-this-week-imd/articleshow/89094938.cms?from=mdr