The phenomenon could create erratic winter conditions impacting agricultural practises during the Rabi season
The ongoing winter season from December 2020 to February 2021 will be colder than usual in several parts of India, according to the seasonal outlook for temperatures from the India Meteorological Department (IMD).
IMD, however, has not made any prediction about the prevalence of cold wave or cold day conditions in any part of the country so far.
Usually, the seasonal outlook for temperatures, issued by the IMD before summer and winter seasons every year, carries predictions for heat waves and cold waves respectively.
Plunging minimum temperatures have led to cold waves in the past. Delhi witnessed its coldest November month in the last 71 years in 2020, recording four cold waves in the period.
While the minimum temperatures in north, northwest, central and some areas in eastern India may be lower than the average, the maximum temperatures in some of the same regions such as north, northwest, eastern and some parts of central India may be higher than the average.
This means that the gap between day and night temperatures will be wider, which could create erratic winter conditions impacting agricultural practises in the Rabi season, especially the growth of wheat that is the principle cereal crop in north, northwest and central India.
It might also affect the productivity of cash crops such as coffee, which grows mainly in south India. The maximum temperatures are going to be lower than the normal and minimum temperatures higher than the normal there. Coffee growth is extremely sensitive to variations in temperatures.
One reason for this could be the prevailing La Niña conditions in the Equatorial Pacific Ocean. La Niña is the cooling phase of the El Niño Southern Oscillation cycle in the equatorial Pacific Ocean, as opposed to the warming El Niño phase.
It is characterised by the unusual cooling of the central and east-central equatorial Pacific Ocean. It usually brings in colder than normal winters in India.
“La Niña influences the Indian subcontinent by piping in cold air from Siberia and South China, which interacts with the tropical heating to produce a north-south low-pressure system,” said Raghu Murtugudde, climate scientist at the University of Maryland.
“The cold air associated with this north-south trough tends to extend much farther south into India. This is remarkably different than the more northwest-southeast blast of cold air associated with an El Niño. In general, the La Niña cold air occupies a larger part of India than the El Niño cold air,” he added.
The pressure pattern going north-south means lesser impact of western disturbances. The cold temperature can go down as far as Tamil Nadu, but may not affect the North East that much.
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