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Monitoring the Monsoon

Fulbright-Nehru scholar Amit Tandon works to improve monsoon forecasts for South Asia.


In India, as in most parts of Southeast and South Asia, monsoon winds—their timely arrival and dispersal—can make or break a farmer’s life. The economies of the countries on the monsoons’ paths are affected as well, so much so that weathermen in India, for instance, release predictions of a “good” or an “insufficient” monsoon to forewarn citizens and government agencies, so that they can take necessary measures. Thus, accurately predicting the monsoon’s mood in the coming season is of utmost importance.

Amit Tandon, a professor of mechanical engineering at the University of Massachusetts Dartmouth and a 2017-2018 Fulbright-Nehru senior researcher, is involved in a project that aims to develop a better model for predicting monsoons in South Asia and improve global weather forecasts. He leads a team of scientists from different countries. The project is also supported by the Office of Naval Research, an executive branch agency within the U.S. Department of Defense.

Tandon conducted his four-month fellowship research titled, “Studying the Impact of Ocean Mixing, Oceanic Fronts and Air-Sea Interaction in the Bay of Bengal for Reliable Intra-Seasonal Prediction of South Asian Monsoons,” at the Indian Institute of Science in Bengaluru.

This year, Tandon and his team sailed on the research vessel Thomas G. Thompson, owned by the Office of Naval Research, on the choppy waters of the Bay of Bengal to examine various aspects of monsoon winds. Asked why they chose this particular region, Tandon explains, “The Bay of Bengal is where the summer monsoon originates. Even though the surface winds come from the southwest, the rainbands and the clouds associated with those rains originate in the Bay of Bengal for much of India.”

He goes on to add, “The winds during the summer monsoon, at lower heights and at sea level, have a constant direction; they come from the southwest for much of the summer monsoon and they reverse direction during the winter.”

Today, however, questions are being raised if these regions are over-dependent on the monsoon, especially in the context of climate change.

Tandon agrees that India is certainly “very dependent” on the monsoon. He adds that there is robust evidence to suggest that monsoons are showing significant rising trends in the frequency and the magnitude of extreme rain events. There is also a decreasing trend in the frequency of moderate events over central India during the monsoon season. “This is cause for tremendous concern, from being ready for intense rain events and floods to paucity of rain in between, in terms of agriculture as well as emergency preparedness,” says Tandon.

One can look at recent reports about geological findings in the Krem Mawmluh caves in Meghalaya, which show how a massive drought in the Holocene epoch, the current period of geological time, led to widespread migration, including in India.

“Technically, a 10 percent variation in monsoon rainfall leads to what is called a flood or a drought year. So, such seemingly small variations in monsoons are very intense and significant on a national scale. A 20 percent decrease or increase could cause havoc for society,” says Tandon.

So, as the monsoon gets increasingly erratic, how will his research track or predict its onset? “This research will help determine the fundamental reasons why the forecast models cannot accurately predict the monsoons 7 to 14 days in advance. Such forecasts from all forecast centers in India, the United States, Europe, Australia, etc. have large errors at this time,” he says.

“Globally, we can’t make reliable predictions more than 10 days ahead. Understanding the science of the monsoons is critical to generating the two-week weather predictions. However, these forecasting challenges have been unsolved for at least 100 years. As scientists and engineers, we have to keep trying our best to allow nature to open up her secrets to us,” says Tandon in an article on the University of Massachusetts Dartmouth website.

“It’s a privilege to study and probe nature in this way,” he says, “to try and coax the atmosphere and ocean system to reveal its way of working to us.”

 

Ranjita Biswas is a Kolkata-based journalist. She also translates fiction and writes short stories.