Tamil Nadu district receives 96-cm rainfall in 1 day; experts link it to climate crisis
The northeast monsoon is Tamil Nadu’s chief rainfall season, but it is associated with tropical cyclones, flash floods and widespread distress
While the annual rainfall for Thoothukudi district is 70 cm, Kayalpattinam in the district received a whopping 96 cm in a single day astonishing meteorologists who linked it to several factors including climate change.
Such heavy rainfall of more than 60 cm and 90 cm is usually associated with well-marked systems such as cyclonic storms. However, this isn’t the case and the rainfall was brought by an upper air cyclonic circulation over the Comorin area. “There was more moisture inside the system which gave widespread rainfall but usually upper air circulation doesn’t give this much rain,” said S Balachandran, head, regional meteorological centre (RMC) in Chennai. “This (system) has given more rain than a cyclone. We have to expect such types of events because of climate change. Research has been published that climate models are indicating an increase in the number of extreme precipitation events in coming years during the north east monsoon season particularly in the southern peninsular region.”
While Chennai has a precedence of extreme rainfall and flooding in 1943, 1976, 1985, 1996, 2005, 2015 and cyclone Michaung related heavy rains, since December 4 this year, there is no such extreme rainfall pattern observed in the southern belt of Tirunelveli, Thoothukudi, Tenkasi and Kanyakumari, said experts. “This is a dry belt which has a semi-arid climate. In the past, this belt has recorded only 20 cm of rainfall in a day,” says former deputy director general of the Indian meteorological department (IMD) YEA Raj. “This rainfall is both unusual and unprecedented especially when we are in the fag end of the north east monsoon. Nothing like this has happened in more than 100 years,” he added.
The northeast monsoon (October to December) is Tamil Nadu’s chief rainfall season contributing more than 40% of its annual rainfall, but it is associated with tropical cyclones, flash floods and widespread distress.
The torrential rains which began on Sunday and continued to Monday is the highest ever rainfall recorded in Tamil Nadu’s plains in 24-hours and the second highest after Manjola in Thoothukudi recorded 965 mm in 1992, said independent weather blogger Pradeep John. That was caused by a cyclone bringing heavy rainfall in the upper catchment area of the Thamirabarani river. “After that, I think this is the heaviest spell,” says John. “Hills happen to record 60-90 cm rainfall but it is very rare for such rainfall in plains.” However, John says that a singular extreme rainfall event cannot be attributed to climate change. “It was a slow moving circulation over the Comorin area so the convergence kept happening repeatedly at the same spot is one reason which resulted in this rainfall,” says John adding that it was similar to the slow movement of cyclone Michaung which struck Chennai on December 4 bringing 500 mm rainfall in 36 hours. “Kayalpattinam’s annual rainfall is 700-800mm so they have got their entire annual rainfall in a single day with 945 mm. This is an extreme and unique event and there is no pattern to which it can be compared. We need to study the cause of this.”
Since IMD’s observatory isn’t there in Thoothukudi, the state government’s observatory has given this rainfall data to the National Data Centre in Pune compare previous years rainfall data in these areas, so they are yet to verify the records broken by this single day’s rainfall in this district, said Balachandran.