Chennai: Researchers from the Indian Institute of Technology Madras (IIT Madras) and Gauhati University have developed a new method to identify the actual onset of the monsoon by distinguishing temporary local rainfall from the establishment of a larger, connected monsoon system.
The study uses a climate-network approach to track how rainfall begins at different geographical locations and how these local events connect to form a wider monsoon pattern. The findings have been published in the Journal of Climate, a peer-reviewed scientific journal.
The researchers treated geographical locations as individual nodes in a climate network. They then examined how clusters of rainfall onsets grow, move and connect across the country.
Under the proposed method, the large-scale onset of the monsoon at a location is identified when its local rainfall becomes part of the largest interconnected cluster of rainfall onsets. This helps distinguish sustained monsoon activity from short-lived rain spells caused by local weather conditions.
The research draws on 84 years of rainfall data. Based on the analysis, the researchers found that the climatological large-scale onset occurs around May 15 over northeast India and June 9 over the Indian peninsula.
Prof. R.I. Sujith, Head of the Centre of Excellence for Studying Critical Transitions in Complex Systems at IIT Madras, explained that the first rainfall experienced at a location does not necessarily indicate the arrival of the monsoon system.
Prof. B.N. Goswami of Gauhati University said the method is intended to complement existing operational definitions rather than replace them.
The findings could have practical applications in agriculture, water-resource management, food security and flood preparedness. A clearer understanding of monsoon onset may help farmers and planners make more informed decisions about sowing schedules and water availability.
The research demonstrates how climate-network analysis can provide another scientific tool for understanding India’s complex monsoon system.
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