New Delhi, May 7 -- Monsoon systems around the world - including India's southwest monsoon, which delivers over 70 per cent of the country's annual rainfall - possess physical memories in the form of stored water vapour, according to a study published on May 6, 2025 in the journal PNAS by the Potsdam Institute for Climate Impact Research (PIK), Germany.

The onset of monsoons in spring or 'switching on' and their retreat or 'switching off' in autumn appeared to depend not solely on incoming solar radiation, as previously believed, but also on the cumulative build-up of atmospheric moisture over time, the researchers found.

"It allows monsoon systems to flip between two stable states. Disrupting this delicate balance would have severe co...