Cold wave: Definition, impacts & NDMA guidelines

Cold wave, heavy snowfall/rainfall, fog, snowstorms etc. have emerged as major weather hazards in recent years affecting different parts of the country. World Meteorological Organization indicates that global temperatures are substantially unveiling variations during various seasons and have a large impact on environment, agriculture, health, livestock, livelihoods, socio-economy and other allied sectors. 
Many countries experience cold wave as a recurrent hazard have developed institutional measures to prepare, mitigate, and respond to cold waves.

Normally, in winter months, after passage of western disturbances, dry cold north-westerly winds make way into north & central India. As a result, minimum temperatures drop over the region and sometimes cause cold wave conditions.

A cold wave is a meteorological event generally characterised by:

  • Sharp drop of air temperature near the surface, leading to extremely low values.
  • Steep rise of pressure.
  • Strengthening of wind speed; or
  • Associated with hazardous weather like frost and icing.

Definition of Cold Wave and Frost As per IMD, Cold Wave and Cold Day conditions are defined as: 

  1. Cold Wave: It should be based on actual minimum temperature of a station. Cold Wave is considered when minimum temperature of a station is 10°C or less for plains and 0°C or less for hilly regions.
    • Based on Departure
      1. Cold Wave (CW): Negative Departure from normal is 4.5°C to 6.4°C 
      2. Severe Cold Wave (SCW): Negative Departure from normal is more than 6.4°C
    • Based on Actual Minimum Temperature (For plain stations only)
      1. Cold Wave: When minimum temperature is ≤ 04°C 
      2. Severe Cold Wave: When the minimum temperature is ≤ 02°C Cold Wave conditions for coastal stations – When minimum temperature departure is -4.5°C or less over a station, “Cold Wave” may be described if the minimum temperature is 15°C or less.
  2. Cold Day: It should be considered when minimum temperature is 10°C or less for plains and 0°C or less for hilly regions.
    1. Cold day: Maximum Temperature Departure is -4.5°C to – 6.4°C 
    2. Severe Cold day: Maximum Temperature Departure is < -6.4°C 
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Factors for Cold Wave occurrence over India 

  • A build-up of a ridge (an extended area of relatively high atmospheric pressure) in the Jetstream over northwest Asia. 
  • Formation of surface high-pressure over north & central India. 
  • Movement of cold air masses in response to steering by upper-level winds. 
  • Triggering mechanisms like a strong westerly wave approaching northwest India to enhance winds for transporting cold air southeastward; and 
  • Extensive snow covers over northwest Himalayas.

Impact of Cold Wave in India

In recent years, occurrences of extreme low temperature in association with incursion of dry, cold winds from north into the sub-continent known as cold waves, cause discomfort, illnesses and even loss of lives. Cold wave occurs in months of December-January every year and sometimes extended cold wave events occur from November to February and are limited mostly to northern India. Cold wave is marked by a well-defined and prolonged period of lower temperatures. Precise criterion for a cold wave is determined by the rate at which temperature falls and minimum to which it falls. Minimum temperature dependents on geographical region and time of the year.

Health: Impact of cold wave on human beings can lead to death or injury. Mortality rates show a marked increase in areas with recurrent cold waves. Health issues are observed more commonly Frost the elderly and neonates.
Agriculture: Cold wave and frost is a major factor that influences crop, horticultural plantations/orchard growth and productivity and has a significant impact on agriculture.
Livestock: A cold wave can also cause death and injury to livestock. During a cold wave, animals require a higher intake of nutrition which affects the hormonal level and efficiency of production.
Fisheries: Extreme climatic conditions particularly in winter months when air temperature drops to 2-4°C and water temperature is between 10-15°C, adversely affects the growth of Indian major carps.
Transport: Cold wave or extreme cold weather affects the transport sector such as airways, river & seaport, roadways, railways, local transport etc.
Energy or power: Energy or power sector receives too much pressure during extreme winter or cold wave season. During cold wave season, energy consumption rises significantly.
Water: Water sector is directly impacted by cold waves as it gets frozen due to extreme low temperature. Due to freezing, water supply may get disrupted.

NDMA Guidelines

  • Hazard, Vulnerability and Risk Analysis
  • Hazard Analysis 
  • Vulnerability Analysis 
  • Risk Analysis 
  • Early Warning and Communication 
  • Early Warning and Forecast 
  • Impact Based Forecast-Warning for Cold Wave 
  • Early Warning Dissemination and Communication Strategy 
  • Prevention and Mitigation measures 
  • A detailed action plan to tackle cold wave illnesses well in advance of winter months.
  • Improving livestock feeding practice and dietary additives
  • Deployment of adequate number of veterinarians and para- veterinarians in cold prone areas
  • To provide shelter to the homeless in Rain Baseras/Vishram Grah throughout the year
  • Advisories and Early Warning: Timely advisory and early warning in coordination with IMD can prevent likely loss of lives or damages due to cold waves. 
  • Health and Medical Facilities: Saving loss of lives and preventing cold wave related illnesses are top priorities; adequate health and medical facilities are necessary to deal with cold wave impacts. 
  • Agriculture: Impact of cold waves on Agriculture is huge and significant. Protection of crops and plants from cold wave / frosts is crucial. 
  • Animals and Livestock: Protection of animals and livestock is also important as they are part of livelihood for large number of households. 
  • Energy: Role of Power/Energy is vital in management of cold waves. Uninterrupted power supply helps in keeping the internal environment warm and helps in medical and health services. 
  • Information Education and Communication (IEC) Dissemination of Warning Messages: Cold Wave related IEC should aim to reach the last person as soon as possible.
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