Fresh Water Could Be Missing Link in Accurate Monsoon Prediction

Scientists have discovered a potential link between the amount of fresh water in the Indian Ocean and the unpredictability of monsoon habits. Normally, monsoon rain falls across South Asia and occurs between June and September, accounting for up to 70% of the region’s annual rainfall.

Monitoring and predicting these monsoon storms are vital to providing adequate contingency plans in the event of mass flooding and also harvesting the rain for use as drinking water, sanitation supplies and irrigation purposes. Indeed, weather monitoring has never been more important than in today's world, especially with the growing threat of climate change.

However, in recent years, estimates about the frequency and intensity of monsoons has been inaccurate. This year that trend is expected to continue, with June already enduring more extended periods of rainfall than forecast and July and August predicted to have less than normal amounts of rainfall.

Freshwater the Possible Cause

Scientists from around the world, including India and the USA, have been working together to develop a hypothesis as to why monsoons are behaving unpredictably – and think they may have struck upon the answer in the shape of the freshwater content of the Bay of Bengal.

“The fresh water makes the surface layer of the ocean water much thinner and lighter and that reacts with the monsoon clouds more strongly; whereas saline water would do so more slowly and that would have less effects on the monsoons,” explained Professor Eric D'Asaro, an oceanographer at the University of Washington in the USA. “And that's one of the reasons they are not able to forecast what are known as monsoon breaks - in other words, the variations on monthly time scales through the monsoon season.”

Both the meteorology departments of Bangladesh and Pakistan admit they have not taken fresh water into account when creating monsoon forecasts in the past and that they would welcome such data in future predictions. India also said there was a need for more comprehensive analysis of weather patterns, but was cautious about the reliability of the supposed link.

A Dearth of Data

However, scientists have warned that even should the countries all agree upon incorporating freshwater content into their predictions, the availability of the information is not prevalent enough to be easily accessible.

India has had an uneasy relationships with its neighbouring nations over sharing water resources for many years, and such tension makes collecting the relevant information a sensitive business. “The countries will have to reach an understanding if they really want to understand what fresh water is doing to the salinity of the ocean and the monsoon systems,” remarked Professor BN Goswani, a climatologist from India.

With the region relying on monsoons so heavily for their water supplies, it’s important not only that its properties are better understood and more accurately monitored, but that the water which is collected is safely stored and treated. The article Water Pollution in Asia: A Brief Review of Monitoring Technologies discusses the different techniques available to the authorities to ensure contamination of water supplies is kept to a minimum.