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Onmanorama Explains | What brought monsoon down to a trickle in Kerala

Erratic rainfall, chaotic crop cycles and half empty reservoirs - these make up the new normal in Kerala as the southwest monsoon is reduced to a trickle after lashing out in a few intermittent spells early on in the season.

The India Meteorological Department (IMD) had predicted a normal monsoon for the country in 2023 despite the prevalent El Nino conditions alongside cyclonic disturbances over the Indian peninsula. (Normal monsoon is rainfall in the range of 94 to 106 per cent of the long period average or LPA.) 

That said, almost two months after the onset of the southwest monsoon on June 8, Kerala is staring at deficient rain.

Reports of meek rainfall in the state, and an unexpected surplus in other parts of India, came even as massive heatwaves wrecked life in the Middle East, Europe and elsewhere.

Scientists are now concerned that the fallout of the climate crisis manifesting at present has indeed dealt aberrations in the ocean currents that regulate global weather systems, evolving over millions, if not billions, of years.

Deficit is in the detail

The country moved from 10% deficit rainfall in June to a 6% surplus in July. As of July 30, the overall rain surplus stood at 33% for the northwest region, 14% for central and 6% for south India. East and northeast India had a rainfall deficit of 25%.

In Kerala, the months of June and July typically contribute an average rainfall of 648.3 mm and 653.5 mm respectively out of the LPA of 2,018.7 mm received in the rainy season.

As of August 3, the southwest monsoon rainfall is 37% less than seasonal average in the state. All the districts in Kerala recorded deficient rainfall except Pathanamthitta. Normal rainfall during the monsoon is defined as a variation of 19% below or above the normal value.

Idukki registered the highest deficit (-54%) followed by Wayanad (-49%) and Kozhikode (-48%) districts.

Rainfall statistics. Source: IMD

Missed chance and an anomaly

“Kerala and Tamil Nadu did not receive adequate rainfall in July due to an anomalous subsidence in the region,” Dr Sivananda Pai, scientist at the Environmental Monitoring and Research Centre, India Meteorological Department, told Onmanorama.

A number of low pressure systems moving to the northern peninsula and Central India brought good rainfall to Karnataka, Andhra Pradesh and Telangana in July but missed Kerala and Tamil Nadu, according to the scientist.

“However, the presence of another low pressure system in the equatorial north Indian ocean south of Kerala affected the state's chances of receiving good rainfall. The rising motion from the two convective zones located in the north and south of Kerala caused a subsidence in the region resulting in below normal rainfall,” Dr Pai explained.

kerala rain
File photo: Manorama

Bleak prediction for Kerala in August, September

Dr Pai is of the view that chances are unlikely to improve for Kerala in the coming months.

“We may receive better rainfall in October and November during the northeast monsoon due to El Nino gaining strength,” he said.

Weak El Nino conditions in the central eastern Pacific associated with low rainfall activity in the Indian subcontinent due to warmer sea surface temperature in equatorial Pacific, have strengthened gradually to moderate El Nino now. El Niño is a climate pattern resulting from the unusual warming of surface waters in the eastern equatorial Pacific ocean.

The Indian Ocean Dipole (IOD), characterised by above normal surface temperature in the Indian ocean which is expected to minimise the impact of El Nino, is yet to reach a positive value. There may be a positive IOD in late August but this is unlikely to narrow the rain deficit, researchers further pointed out.

Climate change and rain patterns

Meanwhile, southern Europe was scrambling for cover as intense heatwaves gripped the northern hemisphere. Heatwaves engulfed the United States and China as well. According to researchers at the World Meteorological Organisation, June 2023 was the warmest June in recorded history.

Dr Sabin T P, a scientist from the Indian Institute of Tropical Meteorology, Pune and a contributing author of the IPCC's Sixth Assessment Report told Onmanorama that erratic monsoons are indeed linked to the climate emergency.

“Monsoon is a wind driven circulation. Climate change has impacted large scale winds significantly,” said Sabin adding that there are two factors driving the change in pattern: aerosols and warming of the Indian ocean.

The increasing presence of aerosols in the atmosphere since 1950 has affected the solar insolation received by the central Indian landmass. Solar insolation is the flux of solar radiation per unit of horizontal area for a given locality.

Solar radiation is reflected outwards due to the presence of aerosols. Lower solar energy in the area will affect the thermal gradient between the landmass and the ocean.

In addition, the Indian ocean is experiencing anomalous warming due to the climate crisis.

The two factors reduce the thermal gradient and weaken the monsoon in the long run.

"However, aerosols have reduced after the year 2000 due to sustained climate action by various nations, which is promising. It has helped the African monsoon recover almost completely. Though improving, Indian monsoon is yet to resume the strength it had in the 1950s," Sabin further clarified.

The cyclone and rapid northward propagation of the monsoon resulted in relatively low rainfall in Kerala this time, he added.

According to Pai, meantime, western disturbances affected by the heatwaves in Europe and Middle East led to high rainfall in Pakistan and western India.

“The hot air above America and Europe is a result of warmer temperatures in the Arctic. This hot air interacts with the monsoon and affects western disturbances bringing rainfall. Pakistan and western India received higher than expected rainfall due to this,” Pai said.

Farming at stake

Though the area under kharif sowing was at 8.4%, higher than last year on account of good rainfall last month, erratic rainfall has affected the agricultural activities across the subcontinent.

While heavy rainfall has damaged newly planted paddy in northern states, such as Punjab, Haryana, Himachal Pradesh and Uttar Pradesh, scanty rainfall has delayed the planting of paddy, corn, cotton, soybean, groundnut and pulses in states including Maharashtra, Telangana, Andhra Pradesh, Chhattisgarh, Bihar and West Bengal.

For instance, Idukki and Wayanad districts account for most of the pepper crop in Kerala. The dip in rainfall will negatively impact pepper and paddy cultivation. The deficit of 49% rainfall in Wayanad will surely hit the pepper produce.



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