Context:
Delhi and other parts of northwest India have been reeling under a cold wave spell that set in last week.
- The lowest minimum temperature recorded this month was 1.9 degrees Celsius on January 8, the second-lowest minimum temperature in January in 15 years.
Relevance:
GS I: Geography
Dimensions of the Article:
- What is a cold wave?
- About India Meteorological Department
What is a cold wave?
The IMD marks a cold wave in terms of minimum temperatures – when the minimum temperature in the plains is 4 degrees or less or when the minimum temperature is less than 10 degrees and 4.5 to 6.4 degrees below the normal.
Major factors contributing to Cold wave
Colder than Normal Temperatures in North India Due to Longer Duration of Fog
- One of the major factors contributing to colder than normal temperatures over north India this month is the large-scale fog cover.
- The fog cover is lasting for longer durations, preventing sunlight from reaching the surface and affecting the radiation balance, resulting in no heating during the day time and impacting cooling even at night.
- Light winds and high moisture near the land surface have been contributing to the formation of a blanket of fog over large swathes of the Indo-Gangetic plains in the morning.
Westerly and Northwesterly Winds and Absence of Western Disturbances Contribute to Low Temperatures
- Westerly and northwesterly winds of around 5 to 10 kmph in the afternoon have also been contributing to the dip in temperature.
- Since there has not been any significant impact of western disturbances over the region, cold northwesterly winds have also been contributing to low temperatures.
- Western disturbances, which are storms from the Mediterranean region, are associated with a change in wind direction, bringing easterly winds to northwest India, which have not been seen since December 29.
Cold Wave Spells in Delhi in December and January
- Delhi usually records cold wave spells in December and January. Over the past decade, the number of cold wave days in January has ranged from none to seven.
- While there were no cold wave days in December in Delhi this winter, the five such days so far this month are more than January last year, when there were no cold wave days, IMD data shows.
- In January 2021, there were 7 days when the minimum temperature was 4 degrees or less, but they were not consecutive. A similar long spell was recorded in 2013, when there were 7 consecutive cold wave days.
About India Meteorological Department
- The India Meteorological Department (IMD) was established in 1875 and operates under the Ministry of Earth Sciences.
- IMD serves as the National Meteorological Service of India and is the primary government agency for all matters related to meteorology and related fields.
Objectives of IMD:
- To take meteorological observations and provide current and forecast meteorological information to support weather-sensitive activities such as agriculture, irrigation, shipping, aviation, offshore oil exploration, and more.
- To issue warnings for severe weather phenomena like tropical cyclones, norwesters, duststorms, heavy rains and snow, cold and heat waves, etc., which can cause destruction of life and property.
- To provide meteorological statistics needed for various sectors including agriculture, water resource management, industries, oil exploration and other nation-building activities.
- To conduct and promote research in meteorology and related disciplines.
-Source: Indian Express
