COLD WAVE
1. Context
In Delhi, the Safdarjung weather station, which provides representative figures for the city, has recorded cold wave conditions for five consecutive days so far this month, making it the longest such spell in a decade. The lowest minimum temperature recorded this month was 1.9 degrees Celsius on January 8, the secondlowest minimum temperature in January in 15 years.
2. What is a Cold Wave?
According to the IMD, cold wave conditions occur when the mercury falls below 10 degrees Celsius in the plains, and the minimum temperature stays at least 4.5 degrees to 6.4 degrees Celsius below the normal level.
2.1 Conditions
- Inflow of cold air mass from higher latitudes over the region in the rear of the passage of a well marked low pressure system in the westerly wind flow of mid-latitudes.
- Foggy weather during the day which inhibits day warming of the region.
- Strong radiation cooling during the night under clear sky conditions.
3. Cold waves in India
Cold waves over the country are generally experienced during December -February. The frequency of occurrence of cold waves is over northwestern parts of India. Occurrence of cold waves is associated with the inflow of very cold air from extreme northwestern parts of the Indian-subcontinent or even beyond.
4. Reasons Behind Cold Wave Conditions in India
4.1 Impact of Western disturbance: Cold wave conditions form due to lack of western disturbances. Western disturbances create precipitation and bring down day temperatures, but night temperatures remain steady.
4.2 Snowfall in the upper Himalayas: This creates a wind chill factor for the northern states of India
4.3 Downward subsidence of cold air: Subsiding air (from the upper Himalayas) further cools down creating low-temperature conditions over North India for a longer period.
4.4 La Nina is known to favor cold waves in North India
It increases the severity of cold conditions, also the frequency and area covered under the grip of a cold wave become larger e.g. winters of October 2020 were colder than usual (2 degrees Celsius, the lowest since 1962) due to the impact of La Nina in the pacific.
5. Impacts of ColdWave
5.1 Impact on Agriculture: It has the potential to destroy the Rabi crop and reduce the production of cash crops (Coffee, Tea). The temperature difference between day and night would be greater.
5.2 Impact on Health: The cold wave is extremely dangerous to human health, and it may impact vulnerable persons (infants, pregnant women, the elderly, and people suffering from chronic diseases). The likelihood of illnesses such as the flu as a result of prolonged exposure to the cold.
5.3 Impact on visibility: A cold wave can reduce visibility, making people more likely to be prone to accidents and lose their lives as a result of them.
For Prelims
| For Prelims: Cold waves, El Nino, La Nina, Indian Meterological Department (IMD), and Western disturbances. |
Source: The Indian Express
