Humid heat waves in India

3rd May, 2024 Environment

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Context:

Heatwaves prevalent in India can be attributed to many conditions such as increase in moisture.

Details:

Heatwave conditions have been prevalent in several regions since mid-April, with Odisha, Gangetic West Bengal, and interior Karnataka experiencing them earliest. Sub-Himalayan parts of West Bengal, Rayalaseema region of Andhra Pradesh, Kerala, Bihar, and the Konkan region of Maharashtra have also been affected subsequently.
The discomfort is not solely due to rising temperatures but also increased relative humidity levels, indicating the presence of moisture in the atmosphere.
Moisture levels in various parts of India are significantly higher than usual, leading to unbearable conditions, particularly in states like Odisha and West Bengal, where humid heat waves are occurring. This is happening because of moisture being pumped in by multiple weather systems over the country, which is being further fuelled by the general warming of the atmosphere and the oceans.

Factors Contributing to Moisture Surge

Cyclonic conditions: Two significant anticyclones over the Arabian Sea and the Bay of Bengal are bringing moisture-laden winds to Odisha, West Bengal, and the Konkan region of Maharashtra.
Anticyclone Influence: Anticyclones, common during the pre-monsoon period, cause heat waves by blocking other weather systems and inducing downward winds that trap heat. Anticyclones result in winds moving from sea to land, increasing relative humidity levels even in inland regions.
Altered Patterns due to Climate Change: Global warming has altered the character of western disturbances, increasing their frequency and causing them to move further southward. This change results in increased moisture transport to western India.
Compounding effect: Climate scientists emphasize the compounding effects of warming temperatures, El Niño, and circulation patterns, leading to rapid evaporation of soil moisture and water bodies, exacerbating humidity levels.

Western disturbance

●A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent, which extends as east as up to northern parts of Bangladesh and South eastern Nepal.

●They are labelled as an extra-tropical storm originating in the Mediterranean, is an area of low pressure that brings sudden showers, snow and fog in northwest India.

●They bring winter and pre-monsoon rain and are important for the development of the Rabi crop in the Northern subcontinent.