A hard rain

  • To minimise the damages caused by monsoon, South Asia needs to study it seriously
- Navin Singh Khadka
A hard rain

Jul 30, 2015-

In the long joint US-India communiqué issued at the end of President Barrack Obama’s Delhi-visit last January, one point was about pursuing monsoon research on the Indian Ocean. It said that the two countries would cooperate in the scientific study of the monsoon with their vessels deployed in the Bay of Bengal.

The Ocean Monsoon and Mixing project has already completed six cruises so far and will be taking more. The research will last until 2017. By then, scientists will bring out their studies on the different aspects of the monsoon. But there is one thing that they have already found and made public: the significant presence of fresh water from rivers and rains in the Indian Ocean.  And they say it could be significantly influencing the monsoon clouds.

Fresh water trail

“Our measurements show filaments of low-salinity water (likely from rivers) and a sharp separation between ‘river’ water and seawater,” says Professor Debasis Sengupta with the Centre for Atmospheric and Oceanic Sciences of the Indian Institute of Science. Oceanographers say such separation could mean a lot in terms of interplay between ocean and the atmosphere above it.  

“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,” Professor Eric A. D’Asaro, an oceanographer at the University of Washington, explained in an interview I did for the BBC recently. As one of the researchers in the Bay of Bengal working with Indian scientists, he believes that factoring in the fresh water could especially help in forecasting what is known as the monsoon breaks—the period between high and low monsoonal rains.

“The real impact of our work will be known only when atmosphere models are coupled to improved ocean models that can generate and maintain the shallow surface layer in the North Bay,” said Professor Sengupta.

Both the researchers say that if the monsoon forecasting models took fresh water into account, the result could be better predictions of monsoonal rains. Meteorologists in South Asia admit they have not been doing that. Met officials from Bangladesh, India, Nepal and Pakistan said it was a vital missing link. If so, the question is why has there been this lapse? Bangladeshi meteorologists say they simply have no idea about it. Those in Pakistan seem to know a bit about it while Indian meteorologists appeared to be aware of it a little more.

To wait or act?

While scientists with Indian Institute of Tropical Meteorology agree that fresh water analysis could be a valuable input in monsoon forecast models, Chief of Indian Meteorology Department, LS Rathore said that the science of the fresh water’s role was not yet clear. He is of the view that research should first make things clearer.

South Asia can well wait for the research results in black and white, although there is no guarantee that there will be a consensus even then. But by then, a lot of more fresh water is sure to flow into the Bay of Bengal, thanks to the rapid meltdown of Himalayan glaciers in the wake of increasing temperatures.

Chinese researchers with the Institute of Tibetan Plateau Research have been warning that glaciers in Tibet have been retreating in an alarming rate.These glaciers feed into the major river systems including the Ganges, Bramhaputra, Meghna and Irrawaddy that all flow into the Bay of Bengal. Scientists say that the layer of fresh water has been found as far as where the Indian Ocean meets the Arabian Sea to the west. And that means the interaction between fresh water and the atmosphere could be happening in a wide area of water. That further raises the chances of influences on the monsoon because that is where the south westerly monsoonal clouds normally come from.

Share data

But to know how much water is actually mixing with the Indian Ocean, you will need annual data from countries through which the rivers flow. That, so far, has not happened because hydrological data are ‘state secret’. Scientists researching on the Bay of Bengal say if countries want to get the monsoon forecasts right, they will have to change their policies.

“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,” said Professor BN Goswami, another Indian scientist with the Ocean Monsoon and Mixing project. Several other factors including climate change, El Nino, and local pollution are already said to be influencing monsoon. Meteorologists say predicting the monsoonal rains is becoming more and more challenging. But the trouble is the influential factors are not being studied properly.

Many years have passed since the United Nations Environment Programme and the World Meteorological Organisation said that both black carbon and ground-level ozone could be disrupting monsoon rains. Scientists in the region, mainly from India, had then argued that the subject needed in depth study and that they would know the facts within a few years. We are still waiting for the results.

Meantime, the monsoon has continued to be more extreme and erratic in the entire region—from Myanmar in the east to Pakistan in the west. To maximise its utility and to minimise the damages from it, a series of serious studies are urgently required. Towards that end, the countries in the region will have to get their acts together. Or else, the monsoon will mean more and more miseries.


Khadka is a BBC journalist based in London  

Published: 31-07-2015 08:02

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