Monsoon 2023 was a story of twists and turns, and highs and lows marked by intense rainfall that wreaked havoc in some parts and dry patches in others, almost raising the spectre of a drought—variations that have flummoxed weather experts. After an eventful season, the monsoon, which began its retreat on September 25, eight days late, withdrew on October 19, four days after the normal date of October 15.
India recorded a cumulative 820 mm rain in the June-September monsoon period, or 94.4 percent of the long-period average (LPA) of 868.6 mm – considered below normal. In 2022, the monsoon was 106 percent of the LPA. It was 99 percent in 2021, 109 percent in 2020 and 110 percent in 2019. Monsoon rain between 96 and 104 percent of the LPA is considered normal, 90 and 95 percent is 'below normal', 104-110 percent is 'excess' and rainfall below 90 percent is 'deficient'.
Though overall monsoon was below normal this year, in July, extremely heavy rain battered north India, causing widespread damage in Himachal Pradesh. (File photo: PTI)
Ups and downs
The monsoon graph was like a roller-coaster ride. June received 151mm of rain against a normal of 165 mm, which is 91 percent of the LPA or 9 percentage points lower. July recorded 315.9 mm against a normal of 280.5 mm – 113 percent of the LPA or 13 percentage points excess, IMD data shows. In July, extremely heavy rain battered north India, causing widespread damage in Himachal Pradesh and floods in Punjab and parts of Delhi after 45 years.
August, the driest month in 122 years, was 36 percent deficient with 162.7 mm rain, which is 64 percent of the LPA of 254.9 mm. September received 184.8 mm against a normal of 164.3 mm, which is 113 percent of the LPA or 13 percent excess.
August had 20 break monsoon days but Himachal and Uttarakhand were again battered by extremely heavy rain in short spells that caused immense destruction.
Even though September recorded surplus rain, there was 11 percent deficiency over northwest India; 25 percent deficiency over east and northeast; 49 percent excess over central India and 26 percent excess over peninsular India.
Region-wise, there was an 18 percent deficiency over east and northeast India in the overall monsoon season; an 8 percent deficiency over the Southern Peninsula; no deficiency over central India and 1 percent excess over northwest India.
Of the 36 meteorological subdivisions, three – West Rajasthan, Saurashtra and Kutch and the Andaman and Nicobar Islands – constituting 9 percent of the total area of the country received excess – while 26 subdivisions with 73 percent of the total area got normal rainfall.
Seven subdivisions – Nagaland, Manipur, Mizoram and Tripura, Gangetic West Bengal, Jharkhand, Bihar, East UP, South interior Karnataka and Kerala – comprising 18 percent of the total area received deficient seasonal rainfall.
Region-wise, there was 18 percent deficiency over east and northeast India in the overall monsoon season; 8 percent deficiency over the Southern Peninsula; no deficiency over central India and 1 percent excess over northwest India. (Photo by Mike Kotsch via Unsplash)
Increase in variability
While the monsoon system has always been unsteady in nature, in recent times there has been an increase in the variability factor, experts say.
“Earlier there would be continuous rain for two-three days due to the Altostratus or medium clouds. But now we see more convection clouds because of which short but intense weather activity has become common, leading to cloudbursts, flash floods, and waterlogging,” says Mahesh Palawat, vice-president of private forecaster Skymet.
Rainfall patterns, Palawat says, are changing over the past eight to 10 years. “Patchy rain is now more common.” Some areas in one district get moderate to heavy showers while others remain dry,” he says.
The onset of this year's monsoon was disrupted by Cyclone Biparjoy, which caused a 15-day delay in the southern and central regions, explains Group Captain SN Mishra, visiting professor, Climate Change and Mitigation, TERI School of Advanced Studies.
However, by the last week of June, the monsoon revived and rapidly covered the entire nation, resulting in a rare simultaneous onset over Delhi and Mumbai on June 25 – two days early in the national capital and after a two-week delay in the financial capital.
“July recorded surplus rainfall, marked by multiple cloudbursts in Himachal and other northwestern parts of the Himalayas, leading to fatalities and extensive damage.”
Northwestern India also experienced excess rainfall, leading to flooding in the Beas and along the Yamuna River and in the Delhi National Capital Region, Mishra explains.
Most scientists agree that climatic change is one of the factors behind the extreme variation. “Yes, we can attribute it to climate change. Rainfall is getting skewed. Some areas remain rain-deficient while others get heavy and excess rain,” Palawat says.
In the Indo-Gangetic plains, there was deficient rain until September. Then, at the fag-end of September, a weather system over the eastern parts brought back rains. But overall, rainfall was deficient in the east while the central parts are getting more rain, Palawat explains.
Mishra concurs, saying climate change is not only causing more frequent and intense extreme weather events but also altering weather patterns, leading to increased intra-seasonal variability in monsoon rainfall.
A dry June and August and a wet July and September condensed monsoon rainfall into just two months and brought about both drought-like conditions and floods, Mishra said. “Rainfall activity spanning four months has been condensed into just two months and this is a cause for concern.”
Raghu Murtugudde, a visiting professor at IIT Bombay and emeritus professor at the University of Maryland, says climate change is hammering the Indian Ocean and the monsoon from all sides – all tropical oceans and the poles. But most importantly, the Middle East warming is causing monsoon wind changes over the Arabian Sea and rapid warming.
“This warming has a huge impact on the monsoon, especially the heavy rains in the north-northwest. This year was weirder because of the early impact of cyclones on the monsoon trough, which allowed moisture from the Arabian Sea to pound Himachal and Uttarakhand,” Murtugudde says.
According to Pai, the impact of climate change on rain is exacerbated by many factors such as population increase, pressure on resources and land, human activity, etc. “An increase in population means providing food to that many people, which means clearing of land and trees for agricultural use, which directly hits the environment.”
A population rise also means an increase in housing needs. “People are inhabiting vulnerable areas such as the hills. This leads to concretization, because of which rainwater doesn’t percolate inside the soil. Intense rain because of climate change means heavier flow of water, which destroys everything in its way,” Pai says.
The El Nino factor was visible in the month of August but was negated in September because of a positive Indian Ocean Dipole (IOD) as well as Madden Julian Oscillation (MJO). (File)
El Nino factor
This year, there was an El Nino factor too, which was visible in the month of August but was negated in September because of a positive Indian Ocean Dipole (IOD) as well as Madden Julian Oscillation (MJO).
“There was an El Nino impact in August, but in September, the tide turned because of a positive IOD and a favourable MJO location,” Pai says.
In simple terms, the warming of the central and eastern tropical Pacific is referred to as El Niño. The phenomenon has the potential to impact weather systems across the world, including the southwest monsoon in India.
The Indian Ocean Dipole is the difference in sea surface temperature between two areas (or poles, hence a dipole) such as the western Indian Ocean and eastern Indian Ocean. MJO is an eastward moving pulse of cloud and rainfall near the equator that recurs every 30-60 days.
According to Palawat, though sea surface temperatures were increasing over the Eastern Pacific because of El Nino, it did not reflect in the atmosphere, so rain activity was decent in July. “The impact was more visible in August, the driest in 122 years. A positive Indian Ocean Dipole and other factors offset the impact and led to significant rain in central and east India,” Palawat says.
Mishra says while El Niño typically has a negative impact on monsoon rain, there have been instances where it had no apparent impact, and this year seems to be one of those. Despite a more pronounced El Niño presence, July and September experienced excessive rainfall, suggesting it did not significantly affect monsoon rainfall, he says.
However, El Niño, Mishra explains, is expected to influence temperatures. “This July, August and September were the hottest months. It is anticipated that global warming, coupled with El Niño, could exacerbate warming, potentially breaching the 1.5 degree Celsius threshold temporarily during this decade itself.”
Forecasters concerned
Apart from causing devastation as well as distress to the farm economy, the changing rain pattern is posing a challenge to weather forecasters.
“The extreme weather is indeed a challenge. Nowadays every forecast for rain is in the range of 50 nautical miles. Earlier rainfall used to be more uniform over a wide area,” Palawat says.
Weather models, Palawat explains, have to be fine-tuned according to changing patterns and conditions. Short-range forecast is as good and accurate as previous years but the long-range forecast for 2-3 months is getting more challenging.
“Not just monsoon and long-range forecasts, winter and heat wave forecasts are also taking a hit,” Palawat says.
The intensification and increased frequency of extreme weather events have rendered past data and experiences insufficient for accurate forecasts, Mishra explains. “The new normal is a challenge for forecasters.”
The intra-seasonal variability of this year's monsoon, which although difficult to predict, has brought about an unprecedented variation. “No one anticipated the typical four months' worth of rainfall to be condensed into just two months,” Mishra says.
Long-term forecasting remains a challenge, particularly for a complex system like the southwest monsoon, as it involves the interplay of various planetary-scale systems, the full impact of which is not yet completely understood, he says.
The real challenge, Mishra says, lies in effectively delivering and interpreting short- to medium-term forecasts to end-users, government authorities, and farmers.
The monsoon is one of the key drivers of India’s economy and as more than half of the cultivated areas are rain-fed, large variations are a challenge for farmers. (Photo by Denniz Futalan)
Adaptability is key
Murtugudde says extremes are being forecast reasonably well but decisions have to be made for disaster management as well as for building resilience in construction and infrastructure. “This is much more of a governance problem.”
Climate forecasts, Murtugudde says, have to get better at seasonal timescale for better planning of water, agriculture, and energy, and for multiple years to a decade for better resilience building.
According to Pai, while there is always a scope for improvement, there will be a limit to what one can forecast. He stresses the need to focus on adaptability and resilience.
The good news is, despite the highly variable monsoon, the country did not experience water stress much and reported an overall successful kharif crop, Mishra says.
The monsoon is one of the key drivers of India’s economy and as more than half of the cultivated areas are rain-fed, such large variations are a challenge for farmers.
Some regions faced deficit rainfall and drought-like conditions, but the impact was minimal, Mishra says. “The copious rains in September and extended rainfall in October compensated for the earlier shortfall and replenished soil moisture, auguring well for the rabi crop.”
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