Coldwave

What are Coldwaves and what are their impacts? What are the major factors leading to cold waves in India? Read further to know more.

Delhi typically experiences cold spells in December and January. Over the past decade, the number of cold wave days in January has ranged from none to seven.

What is Coldwave?

The coldwave conditions denote a certain percentage fall in temperature from the normal climatological value at a particular location. Cold wave (CW) conditions generally occur in India from November to March.

During this period, the health of people is severely impacted. Particularly, poor people’s health conditions are negatively impacted, and in the worst circumstances, it can even result in serious casualties.

A cold wave is a localized seasonal phenomenon prevalent in the country except in southern India. The northern parts of India, especially the hilly regions of Jammu and Kashmir, Himachal Pradesh, Uttarakhand, and the adjoining plains are influenced by transient disturbances in the mid-latitude westerlies which often have weak frontal characteristics.

States like Punjab, Rajasthan, Delhi, Haryana, U.P., Bihar, and Jharkhand are highly affected by the cold wave.

Coldwave Classification

As per the India Meteorological Department’s criteria, Cold Wave and Cold Day conditions are defined as:

Coldwave: It should be based on the actual minimum temperature of a region. Cold Wave is considered when the minimum temperature of a station is 10 degrees 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 the minimum temperature is ≤ 04°C
2. Severe Cold Wave: When the minimum temperature is ≤ 02°C

Cold Wave conditions for coastal stations

When the minimum temperature departure is -4.5°C or less over a station, a “Cold Wave” may be described if the minimum temperature is 15 degrees C or less.

Cold Day: It should be considered when the minimum temperature is 10 degrees 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

Core Cold Wave Zone- Hazards Analysis

The northern regions of the country, the Himalayas, and the western desert regions are particularly prone to cold waves.

• In the current climate change regime, these weather-related events (like cold waves) are further aggravated.
• According to IMD, India’s ‘Core Cold Wave Zone’ covers 17 States/UTs. With a total population of 90.90 crores residing in these 17 states/UTs are falling under the Core Cold Wave Zone.

The Major Factors for Cold Wave Occurrence in India

Usually, the condition of coldwave in India occurs for the following reasons:

• A build-up of a ridge (an extended area of relatively high atmospheric pressure) in the jet stream 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 the transport of cold air southeastward; and
• Extensive snow covers over the northwest Himalayas.

Why North India Experiencing Colder than Normal Temperature

Major Factors Contributing to Colder than colder-than-normal temperatures Over North India are:

Wind and Moisture Content: Large parts of the Indo-Gangetic plains have been covered in a layer of fog due to light wind and high moisture levels near the land’s surface.

Large-scale Fog Cover: Long-lasting fog interferes with the balance of radiation by blocking sunlight from reaching the surface.

Westerly: westerly and northwesterly winds of around 5 to 10 km/h in the afternoon have also been contributing to the dip in temperature.

Impact of Coldwave

Coldwaves have historically been referred to as “cold weather” and are recognized as seasonal changes in India. Coldwaves were considered a local disaster that received the fewest number of disaster preparedness or mitigation attention because they occur occasionally, only in certain regions of the country.

• Agriculture: Cold waves and frost is a major factor that influences crop, horticultural plantations/orchard growth, and productivity and has a significant impact on agriculture. As a result, the livelihood of people gets adversely affected.
• Livestock: A cold wave can also cause death and injury to livestock. Similarly, wildlife also experiences challenges during winter for both shelter and food.
• Human Health: Cold waves have significant effects on health. It can cause severe lung-related problems like wheezing, coughing, and shortness of breath and is fatal to asthma and bronchitis. It can also cause eye irritation and infection. In India, cold waves have caused 4,712 deaths from 2001 to 2019 across various states.
• Transport and Aviation: Cold waves or extremely cold weather affects the transport sector such as airways, rivers & seaports, roadways, railways, local transport, etc.
• Power Sector: Chances of Tripping of Power lines in the very dense fog routes.
• Economic Loss: There was significant damage to crops, horticulture, forest trees, livestock, fisheries, water supply, power supply, transportation, tourism, social activities, economy, and other livelihood systems in these regions that led to significant economic losses to the farming community.

Measures and Mitigations

Multi-Dimensional Approach: To deal with governance issues related to Disaster Risk Management for coldwaves, there is a need for a multi-sectoral and multi-dimensional administrative approach.

Improvement in the Health Sector: In the health sector, interventions can be introduced to address cold wave impacts.

Early Warning System and Public Awareness: Early warnings are a major element of disaster risk reduction and help in minimizing the loss of lives and economic impacts. An effective early warning system helps the communities at risk by generating public awareness, effectively disseminating warnings, and ensuring there is a constant state of preparedness.

National Level Plan: As there were no guidelines and action plans on cold waves at the national level, it was a challenge for disaster managers to take standardized preventive, preparedness, and mitigation measures.

Preventive Measures: There is a need to prepare an action plan for the cold wave season as a concurrent disaster and take all possible timely actions for preventive, preparedness, and mitigation measures to reduce the impacts of the coldwave.

Read: Marine Cold Waves

Article Written By: Priti Raj