Cold Wave

A Cold Wave is defined as a sudden fall in temperature in the same region and date as compared to its normal temperatures for previous years. “Core Cold Wave Zone” is a zone which frequently witnesses cold waves from time to time. Following states are all part of India’s “core cold wave zone”:

• Bihar
• Chhattisgarh
• Delhi
• Gujarat
• Haryana
• Himachal Pradesh
• Jharkhand
• Madhya Pradesh
• Odisha
• Punjab
• Rajasthan
• Telangana
• Uttarakhand
• Uttar Pradesh
• West Bengal

The topic has a high probability of being asked as a Current Affairs Question and as Geography Questions in IAS Prelims and Mains.

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Facts about Cold Wave

As per the Indian Meteorological Department (IMD), a cold wave in the plains occurs when the temperature drops below 10 degrees Celsius and the minimum temperature falls below 4.5 degrees Celsius. The criterion for hills is that they must be 0 degrees Celsius. In the plains, a severe cold wave occurs when the temperature falls below 6.4 degrees Celsius or falls below 2 degrees Celsius. It’s “a state of air temperature that becomes lethal to the human body when exposed,” according to the IMD. Every five days, the ‘normal’ temperature is computed by computing the mean temperature for all these days over the previous 30 years.

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Causes of Cold Waves

The arrival of cold waves can be attributed to various factors or a combination of some factors. Following are the major causes of cold waves in India:

• Clouds Absence: Some of the outbound infrared radiation is trapped by clouds, which then radiates it downwards, heating up the ground. In the absence of a thick cloud cover, the radiation escapes the atmosphere thereby reducing the surface temperature of the earth in that region.
• Himalayan Snowfall: Snowfall in the Himalayas’ upper reaches brings chilly winds to the region.
• Subsidence: The flow of cold or dry air near the surface is known as subsidence.
• La Nina: Ongoing weaker La Nina phenomenon in the Pacific Ocean. La Nina is characterised by unusually cool ocean surface temperatures along the equatorial Pacific Ocean, which is considered to favour cold waves. The intensity of cold circumstances increases during La Nina years. The frequency of chilly waves increases, as does the region affected.
• Western Disturbance: It is an extra-tropical storm that originates in the Mediterranean area and provides sudden winter rainfall to India’s northern states. These are non-monsoonal in character and westerlies are responsible for their flow to India. The western disturbance usually leads to a sharp fall in temperature due to flowing wind as well as rainfall.

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Consequences of Cold Wave

A cold wave can have very harmful effects upon all kinds of organisms inhabiting the area, some of which are:

• Death and/or injury to livestock/wildlife
• Increase in caloric demand of the body
• Hypothermia in Human Beings
• Crop failure or death of plants

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India Meteorological Department (IMD)

The India Meteorological Department (IMD) was established in the year of 1875 as the country’s national meteorological agency and is the country’s primary government organisation for meteorology, seismology, and related sciences. The Department’s administrative functions are overseen by the Union Ministry of Earth Sciences of the Indian government. New Delhi is the home of the IMD.

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Recent Developments

• IMD has predicted the onslaught of severe cold wave as well as dense fog in the northern and north-western India.

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