117 years of data show Goa saw over 100% increase in heavy rain

PANAJI: With extreme rainfall events showing a disturbing rising streak, the number of rainy days with very heavy and exceptionally heavy rainfall has increased worrisomely by more than 100%, the Goa State Action Plan for Climate Change 2023-33 (GSAPCC) states.
After crunching rainfall figures from 1901 until 2018, scientists and experts observed a slight drop in the frequency of light and moderate rainfall events.
But the rise in the frequency of extreme rainfall events in the state for over a century has been phenomenal. The days of heavy rain have increased by about 60%, and those of very heavy and exceptionally heavy rain have shot up to a disturbing 100%, as per the GSAPCC document.
The action plan was released last week and was prepared by Nabcons, a subsidiary of Nabard, under the guidance of the Goa State Biodiversity Board (GSBB), with a host of adaptation strategies in various sectors.
Several 100+mm 24-hr spells of rainfall recorded
Goa, as a coastal state, is already in the grip of climate change-driven phenomena, ranging from the impacts of rising seawater levels to extreme weather events (EWE).
“Our analysis for the last 100 years of daily rainfall data suggests that in recent decades the rainfall variability, i.e year-to-year variation in rainfall — some years being drought years and some being flood years — has increased significantly,” said Rajiv Chaturvedi, associate professor, Bits-Pilani and a member of GSAPCC.
During the last few seasons, IMD recorded state average rainfall of above 100mm in 24-hour spells on several occasions.
In a few cases, extreme precipitation events are triggered by intense cyclones and a combination of different systems. The frequency of intense cyclones is showing a drastic rise.
“The Indian Ocean (IO) is the warmest among oceans in recent years, and the western equatorial IO and southern Arabian Sea, which are part of it, have been the warmest. This has resulted in a changing pattern of monsoons and cyclones in recent years, which are the two important meteorological phenomena as far as the Indian subcontinent is concerned,” said M R Ramesh Kumar, chief scientist (retired), National Institute of Oceanography, Dona Paula.
During 2019, in an unprecedented episode, five cyclones formed in the Arabian Sea as compared to just three in the Bay of Bengal.
In a disturbed rainfall pattern, offseason rainfall has also shown a significant rise. “Though the GSAPCC has not gone through the increase in extreme rainfall during the post-monsoon season, which we will be doing later, the quantum of precipitation during this phase has also shown an upward trend,” said Chaturvedi.
That October (2019), the rainfall was extremely heavy and the month ended as the wettest in 120 years.
Unseasonal rainfall, along with rising extreme weather events during the season, are likely to be a double whammy for the state. “Increase in unseasonal rain has implications for agriculture, rice production, cashew and mango crops, vegetables, salt production, a number of economic activities, forest phenology, and livelihoods,” said the GSAPCC member.
The GSAPCC report has also carried out future projections on the subject. “What we discussed is from the past 100 years, but going forward, regional climate models indicate a further increase in extreme weather events in the state,” he said.