New Delhi: Rise in surface temperatures due to climate change is likely to boost monsoon depressions over India, which will increase the intensity of extreme rainfall events, says a new research.
The study published in Nature Scientific Reports was carried out by researchers from School of Earth, Ocean, and Climate Sciences, Indian Institute of Technology (IIT), Bhubaneswar, Odisha.
Past studies have shown that there was an increase in the moisture content of atmosphere over India due to consistent increase in surface warming, induced by climate change.
According to the recent data from the European Centre for Medium Range Weather Forecast, the relative humidity in the mid-troposphere has increased about 2% over the sub-continent in last 39 years, which has led to the increase in extreme rainfall events over central India.
Researchers wanted to probe the impact of the changing climatic conditions on four types of monsoon depressions arising from the Bay of Bengal and the Arabian Sea, which are major drivers of the summer monsoon.
“We have clear evidence that moisture is going to increase over the Indian region and, with it, the water holding capacity of the air will also increase, as warmer air can hold more moisture. So to examine their impact on monsoon depressions, we conducted climate change surrogate experiments and found that it was highly likely that intense monsoon depressions will occur in the near future over India," said lead author, Sandeep Pattnaik from IIT Bhubaneshwar.
Researchers highlighted that when a specific depression makes a transition from sea to land, its interaction becomes very complex. This interaction of atmosphere with the land surface and the type of clouds generated due to elevated moisture are big factors to determine monsoon rainfall. However, our prediction models have big uncertainties in representing clouds and cloud formations.
“The atmosphere is getting much warmer due to cloud heating. When the cloud condenses over atmosphere, it releases heat. When that heat becomes stronger, it creates a low pressure, against the bottom layer, which shows high pressure and this creates a gradient. The vertical motion becomes stronger, the storm intensifies, which also sustains depression in a more intense way," Pattnaik added.
Even as the representation of clouds continue to be a key problem in the current weather models, researchers highlight that the current study indicated that under a moist low–mid troposphere over the Indian subcontinent, stratiform or the low-level, stable clouds could be the dominating means through which heat is released into the troposphere that can facilitate intense depressions with enhanced precipitation.
The study remains significant as the summer monsoon brings nearly 80% of annual precipitation between June and September, which is crucial for an agrarian nation such as India.