In an effort to better understand and predict South Asia's seasonal monsoon, British scientists are getting ready to release robots into the Bay of Bengal in a study of how ocean conditions might affect rainfall patterns.

The seasonal monsoon, which hits the region between June and September, delivers more than 70 percent of India's annual rainfall. Its arrival is eagerly awaited by hundreds of millions of subsistence farmers across the country, and delays can ruin crops or exacerbate drought.

Yet, the rains are hard to predict, and depend on a complex interplay between global atmospheric and oceanic movements that is not yet fully understood. They can be affected by weather phenomena such as El Nino. And scientists say they may also become even more erratic with increasing climate change and even air pollution.

"We are aiming for a better understanding of the actual physical processes," said lead researcher Adrian Matthews of the University of East Anglia's School of Environmental Sciences, in a statement released on Tuesday. "Ultimately, the goal is to improve the prediction of monsoon rainfall over India."

As part of the newly launched $11 million study, scientists from British university will spend a month at sea releasing seven underwater robots from an Indian research ship across a 400-km stretch of water.

The torpedo-shaped robots will glide through the water, monitoring its salinity, temperature and current before surfacing and transmitting data to a satellite.

At the same time, scientists from the University of Reading and the Indian government in a related study will take atmospheric measurements at the same time.

By comparing the two sets of data, scientists hope to better understand how ocean conditions affect monsoon patterns.

This year's monsoon arrived at the southernmost tip of the subcontinent on June 8 and has been slow in moving north and providing relief amid a devastating drought that has hit wide swathes of central, eastern and northern India.