Cold Wave

Definition and Thresholds

A cold wave is a weather condition, which includes a sharp drop in the air temperature. India India Meteorological Department (IMD) defines it in relation to the minimum temperature and its deviation to the normal (average) temperature.

• Criteria for Plains:
  • Cold Wave: Minimum temperature is 4°C or less, OR 10°C or less with a departure of 4.5°C to 6.4°C from normal.
  • Severe Cold Wave: Minimum temperature is 2°C or less, OR the departure from normal is more than 6.4°C.
• Criteria for Hilly Regions:
  • Cold Wave: Minimum temperature is 0°C or less and the departure is 4.5°C to 6.4°C below normal.

Geographical and Meteorological Causes

• Western Disturbances: These are extra-tropical storms which occur in the Mediterranean. They introduce rain and snow to Himalayas; the cold winds after such upheavals move over the North Indian plains.
• Snowfall in the Himalayas: The presence of heavy snow cover in the mountains provides cooling of southwards blowing winds.
• Absence of Cloud Covers: With clear skies, the radiation of the earth are released back into space very fast at night, and the air and the ground cool fast.
• La Niña: Cooling of the central pacific ocean tends to bring cold winters in North India.
• Wind Direction: The north-westerly winds constantly bring the freezing air of the Central Asian continent and the Himalayas into the Indian heartland.

Impact of Cold Waves

• Agriculture: Frost (ground freezing) has the capacity to destroy such crops as mustard, peas, and wheat. It leads to “cell busting” in plants as a result of frozen water.
• Human Health: More cases of hypothermia, frostbite and respiratory diseases. It is a serious threat towards the homeless people.
• Economy: Dense fog (related to energy expenditures on heating), consequent delays in transport, and mortality of items (livestock).
• Environment: The environment influences the movement of the birds and the physiological cycles of the flora of the area.

Management strategies for cold waves

1. Early Warning Systems: IMD issues impact-based alerts ( Yellow, Orange, Red ) up to five days ahead to enable state and district governments to draw certain action plans.
2. Infrastructure and Shelters: One of the major plans is to put up and sustain Rain Baseras (night shelters) to the vulnerable homeless groups, where they should be given blankets, heating, and simple facilities during peak winter seasons.
3. Agricultural Mitigation: The government encourages resistant agricultural activities to avoid losses on crops like recommending farmers to use micro-irrigation techniques (to avoid frost-freezing) and shedding wind barriers.
4. Preparedness in the health sector: Prevention can be done by giving warnings on the appropriate dressing, food, and the correct use of heating machinery (to avoid carbon monoxide intoxication). Health departments create health camps related to the winter season and make sure that hospitals are ready about hypothermia and respiratory illnesses.
5. Inter-Agency Coordination: NDMA supports state level CWA plans which involve coordination of activities among state health, power, agriculture, and public works departments so that their efforts are coordinated to respond to the emergency.

Role of NDMA (National Disaster Management Authority)

The NDMA collaborates with the state authorities to devise the Cold Wave Action Plans. These plans are concerned with the inter-agency coordination, constant power supply and the conducting of mock drills during disaster response in extreme winter conditions.

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