Rainfall in Kerala's highlands increased in last three decades

Time of India

26-06-2025

Kochi: Kerala's rainfall pattern is changing again. From the decline recorded over the last several decades, the pattern has shifted with an increase in precipitation in the highlands and midlands of the state.
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However, there is a decline in the coastal areas, a new study by Indian Institute of Tropical Meteorology (IITM), Pune reveals.
The researchers at IITM examined rainfall data over a 30-year span from 1990 to 2020. The highlands have been receiving more rainfall in July, while the lowlands receive more rainfall in June, according to the study published in Climate Dynamics.
The change is evident across the high and midlands of Thrissur, Palakkad, Malappuram, Wayanad, and Kannur.
"This is evident across the entire stretch of Western Ghats. This observation is particularly important given that the Kerala highlands exhibited a significant decreasing rainfall trend during the period from 1901 to the 1980s," said Hamza Varikoden, senior scientist at IITM who is one of the authors of the study.
He said that this pattern signalled a slowdown in the overall declining trend in Kerala's monsoon rainfall since the 1990s.
Contrary to earlier assessments regarding highland rainfall in Western Ghats, recent decades have shown greater rainfall variability and more frequent intense rain events in the highlands of Kerala, said the study titled 'On the slowdown of southwest monsoon rainfall decline in recent decades over Kerala'.
Datasets used in this study for the period 1990 to 2020 include daily rainfall data from 50 rain gauge stations operated by IMD.
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For the 1950 to 2020 period, they used the IMD daily gridded rainfall dataset. The elevation classification of Kerala defined lowlands as 0–30m, midlands as 30–200m, foothills as 200–600m and highlands as above 600m.
Kerala experiences a significant negative trend in July, while Sept showed a marked positive trend. In contrast, June and Aug exhibit insignificant decreasing and increasing trends, respectively. While the state's rainfall changes in recent decades provide some insights into implications on adaptive strategies and agricultural planning for the state, there is also a caveat with the limited availability of observations, particularly in the midland and highland regions of Kerala, the researchers said.
The study indicates a critical need for a larger observation network to further understand the impact of complex mesoscale terrain on zonal variations in rainfall as the climate changes.