How climate change weakened India's defence against heatwaves

India saw its hottest April in almost 100 years, restarting the conversation of how climate change will manifest

A cooling Western Disturbance (WD) is being disrupted due to the changing weather patterns, a result of climate change, exacerbating India's already severe heatwave, according to experts.

To understand what this means, we have to first understand what a western disturbance is and the role it plays in the climate process.

As India is grappling with an unprecedented heatwave, it must be noted that WDs are very crucial during the summer season as they suppress heatwave conditions in the Indo-Gangetic plains, the areas currently worst-hit by extreme heat. WDs drive the weather and govern the wind pattern over regions (both mountains and plains). WD infuses moisture-laden winds over the landlocked northwest region. This further interacts with the humid easterly winds from the Arabian Sea, triggering the formation of weather systems such as cyclonic circulations and troughs, resulting in rain and thundershower activities.

Climate change, however, has led to dynamic changes in the pattern of WDs. Although the frequency of WDs has increased, those have not translated to the precipitation associated with them.

“Global warming can be held responsible up to an extent. WDs are getting lighter by virtue of increasing heat, as it decreases the moisture content. Subsequently, these Western Disturbances are now moving across higher elevation due to heat and are reaching up to Karakoram range. Climate change has made some dynamic changes in the pattern of WD,” A P Dimri, Director of Indian Institute of Geomagnetism, Mumbai told DH.

Feeble cooling WDs in the north led to record temperatures

In the last two months, India witnessed only four WDs travelling through Western Himalayas between March and April. They were feeble in nature and thus, restricted their effect to mountains only. Northern plains recorded very light activity in terms of some passing showers and dust storms around the fag end of April that did not make any impact on the temperature profile.

Meanwhile, this prolonged dry spell paved the way for the continuous flow of hot north-westerly winds from arid regions in association with anticyclones. These hot winds blow unchecked across northwest India and parts of central India and also reach the eastern parts as well. These winds were already blowing from the much hotter region of Pakistan and adjoining Rajasthan, which led to record high temperatures.

Anticyclone, another effect of changing weather patterns, that drives the heat up

Another weather phenomenon, anticyclone, can be defined as a large-scale circulation of winds around a central region of high atmospheric pressure. While a cyclone attracts the winds around it, an anticyclone throws the winds in all directions as it rotates clockwise.

“The anticyclone sent warm winds from north-west to central and western India for a longer duration, causing as well as intensifying the heat waves. In absence of rains, the desert region was already witnessing high temperatures. Not to forget, that winds have been warmer than earlier on account of global warming, hence heat waves are more intense now. This makes Western Disturbances even of more importance for Northwest India, as only they can force anticyclone to dissipate or move further,” said Mahesh Palawat, VP at Skymet Weather told DH.