Monsoon onset likely to be more frequent in May

Although June 1 is traditionally considered the opening of the rainy play successful Kerala, an investigation of southwest monsoon onset information from 1901 to 2025 reveals that the monsoon has predominantly precocious to May successful caller decades owed to assorted factors, including planetary warming. Furthermore, Kerala is experiencing a paradox: portion wide rainfall is declining, isolated utmost downpours are becoming much intense, particularly successful parts of cardinal and bluish Kerala adjacent to the Western Ghats, expanding the hazard of floods.

A insubstantial titled ‘Analysis of Temporal and Spatial Variations successful Extreme Precipitation implicit Kerala,’ published successful the Journal of Agrometeorology by a radical of researchers headed by P.S. Biju, a elder idiosyncratic astatine the India Meteorology Department (IMD), Thiruvananthapuram, on with Raji Pushpalatha of Amrita Vishwa Vidyapeetham and researchers from the National Institute of Technology, Patna, and the Indian Institute of Space Science and Technology, sheds airy connected however rainfall patterns, monsoon behaviour, and utmost precipitation events person changed crossed Kerala implicit a 124-year play utilizing high-resolution regular rainfall information from the IMD.

The survey recovered that the southwest monsoon onset occurs connected mean astir June 1, with a modular deviation of astir six days. However, the onset has predominantly precocious to May, particularly successful caller decades. According to IMD data, from 1901 to 2025, the onset occurred successful May 57 times, portion it occurred successful June 68 times. Considering each disposable information from 1870 to 2025 (156 years), the onset occurred successful May 70 times, portion successful the remaining 86 years it occurred successful June.

Monsoon rainfall down

After the twelvemonth 2000, the onset occurred successful May 14 times, indicating that aboriginal onset of the southwest monsoon whitethorn go much communal owed to clime change. Southwest monsoon rainfall is besides witnessing a decreasing inclination successful Kerala astatine a complaint of 26 cm per decade, though the full fig of rainfall days is expanding and terrible upwind events are rising crossed cardinal Kerala and the Western Ghats regions of bluish Kerala. However, coastal Kerala is showing a alteration successful terrible upwind events similar utmost rainfall, according to the study.

According to Mr. Biju, the onset is gradually shifting towards May owed to planetary warming associated with clime change. Summer temperatures whitethorn emergence successful future, perchance causing the aboriginal improvement of low-pressure systems implicit Kerala. The monsoon winds, which stroke from high-pressure cells adjacent Madagascar, determination towards low-pressure systems implicit onshore aft crossing the equator. Global warming causes the earlier improvement of low-pressure systems implicit land, on with changes successful the monsoon trough and vigor lows. This is 1 of the main reasons for the earlier onset of monsoon, Mr. Biju said.

Summer rainfall up

Average yearly rainfall crossed the State was reported astatine astir 2,920 mm, with important spatial variation. The northeast monsoon besides exhibited decreasing trends. However, summertime rainfall showed a flimsy increase. Variations successful rainfall crossed Kerala are chiefly owed to its topography, particularly the power of the Western Ghats. Northern Kerala receives the highest southwest monsoon rainfall, astir 2,300–3,000 mm, portion rainfall decreases towards cardinal and confederate districts. Some confederate regions grounds little than 1,500 mm during the southwest monsoon. On the different hand, northeast monsoon rainfall is much concentrated successful confederate Kerala.

The changing trends besides constituent to an urgent request for district-specific clime adaptation strategies successful Kerala, improved flood management, amended h2o retention systems, and climate-resilient cultivation readying to assistance header with the State’s changing rainfall patterns, according to the paper.