New Delhi: India’s summer monsoon is undergoing significant changes, influencing not just agriculture – for which the rains are a lifeblood --- but also the length and intensity of the summer.
Recent data from the India Meteorological Department (IMD) shows a trend of weaker monsoon rainfall in June, followed by prolonged, heavy rainfall in September. This shift is accompanied by rising temperatures during monsoon months and an increase in the number of dry days over eastern India.
Scientists say India should prepare for the monsoon’s new character, which is changing when rain falls, where it falls, and with what intensity.
Weaker June rainfall in recent years
Since 2008, nine years saw below normal monsoon rainfall in June and six recorded near normal to above normal rainfall, as per data with IMD. Here, normal is the average rain received during 1971-2020 in June.
Increasingly, June rainfall appears to be either weak or patchy, which means the monsoon properly begins only in July, especially over east, central and northwest India.
At the same time, IMD’s monthly climate summaries also show another interesting trend: Since 2008, in September, when the monsoon is normally expected to wind down, nine years have recorded above normal rain as compared to six with near normal or below normal rain.
For July, seven years saw below-normal rain and eight above-normal. In August, eight years recorded below normal rain and seven above- and near-normal.
M Rajeevan, former secretary of the Ministry of Earth Sciences, said, “We are seeing that there is a tendency of monsoon coming late in June or being weaker in June and then continues well after September. The delay is pronounced over central and east India.”
Rajeevan added that this shift might be linked to delayed western disturbances and Arctic sea ice melting as a result of the climate crisis, though the exact causes remain unclear. “The westerly regime is very strong and the monsoon winds cannot set in properly until that continues. Even this year hot westerlies were blowing over NW India causing extremely high temperatures while the monsoon had stalled around Maharashtra,” he said.
The westerly regime Rajeevan refers to is the pattern of winds that normally blow over the northern part of the country. This system is often punctuated by rain-bearing weather, known as western disturbances, which originate in the Mediterranean and bring rain to the states of Rajasthan, Punjab, Haryana, Delhi, Western Uttar Pradesh and the Himalayan foothill regions.
HT on February 12 reported that though the number of western disturbances impacting India may be increasing as per some datasets, the number of strong disturbances that bring winter rain to northwestern Himalayas are in fact declining, leading to a lower snowpack and dry conditions over higher altitudes.
Weak winter rains appear to further feed into how quickly the summer heats up the north. “It has been observed that there is extended heat in June, when normal temperatures are anyway high, and even July, which of course has a correlation with monsoon onset in June and whether there is a lag following onset or if there are below normal rains during that period. We do not see any major change in the monsoon onset date as such which remains around June 1 over Kerala. Our report indicates, September rainfall is good and a slight declining trend in June and July. This should be correlated with recent five years data,” said Pulak Guhathakurta, senior fellow at Pune International Centre and former head, climate research division of IMD Pune.
OP Sreejith, the head of Climate Monitoring and Prediction Group, cautioned that weakened June rainfall in recent years may be a result of El Nino and La Nina transition years. “High summer temperatures and weak June rainfall in recent years may be a result of El Nino years. If we see 2009–10, 2014–16, 2018–19 (weak El Nino) have been El Nino years. But two things are clear, monsoon months have prolonged and are continuing till October and that there is a decreasing rainfall trend over east and northeast India,” he said.
M Mohapatra, director general, IMD, shared the view: “The weakening trend in recent years is mainly due to deficient rain in 2009 and 2019 El Nino years.”
Down To Earth, a publication of Centre for Science and Environment analysed IMD data for 30 years, from 1988 to 2018, covering 676 of India’s 730 districts in 28 states and the Union Territory of Jammu and Kashmir, to find that 420 districts in the country (62% of the districts covered in the data) have seen a decrease in rainfall in June — the key month for sowing the kharif crop.
This year too monsoon saw a long lag of about nine days after it reached Maharashtra on June 11. It has now picked up gradually but is still about a week late compared to its expected track. The lag led to extremely high day and night temperatures over northwest, east and central India in June.
El Nino is the cyclical warming of the equatorial Pacific region, which triggers a cascading effect on the weather around the world --- in India, it has typically led to a weak monsoon season. The La Nina is the opposite phenomenon and is linked to excess rains over the Indian subcontinent.
Hotter monsoon months and change in spatial patterns
IMD’s reports indicate there is a very clear and steep rise in temperatures during all monsoon months with a particularly alarming trend since 2013. East and northeast India recorded their warmest and second-warmest July in 2022 and 2023 respectively. Central India recorded its warmest and second-warmest Septembers in the past five years.
“Monsoon months are seeing a spike in temperatures. It is a combination of intra-seasonal variability and global warming,” explained OP Sreejith.
Mohapatra said: “Once temperature rises, the relative humidity rises as principle. However, we have not checked the amount of trend in relative humidity.”
According to a report released by IMD on “Observed Monsoon Rainfall Variability and Changes during Recent 30 years” in 2020, Uttar Pradesh, Bihar, West Bengal, Meghalaya and Nagaland have shown significant decreasing trends in southwest monsoon rainfall during the recent 30 years period (1989-2018).
The changing monsoon patterns have significant implications, including how both heavy rainfall events and dry days are becoming more frequent.
But there is also erratic rainfall distribution. There is now a significant increasing trend in the number of dry days during monsoon season over south coastal regions of Andhra Pradesh, Bihar, northern parts of Chhattisgarh, Jharkhand, Madhya Pradesh, Odisha, Tamil Nadu, Uttar Pradesh and West Bengal. All these states, along with Telangana, also show a significant increasing trend in dry days, whereas Gujarat, Karnataka, Maharashtra, Rajasthan and Punjab states show significant decreasing trends in dry days.
The implication for farmers
Ramanjaneyulu GV, executive director of the Centre for Sustainable Agriculture, noted that such trends pose a particular threat to farmers. “ The high heat in both June and July impact vegetables which are most sensitive but more importantly entire cropping pattern is shifting leading to a delay in Rabi crop also.”
Farmers urged preparation for the monsoon’s changing character, especially fearing significant economic consequences.
“This year the largest impact of extreme heat has been on cotton and beans over north India. They have been almost burnt, and are beyond recovery. Wheat has not been impacted as much. But increasingly farmers are dealing with extreme heat in initial months and then floods in the later part of the monsoon. But, there is no plan on how to minimise these impacts,” said Lakhwinder Singh Aulakh, president of the Bharti Kisan Ekta (Haryana).