Role of Arctic Warming on Extreme Cold Weather Conditions in North India

Cold waves are characterized by a sharp drop in air temperatures that lasts for a few days, impacting various sectors of society, including human health, agriculture, and transportation. In India, the northern parts of the country witness the majority of cold wave events during boreal winter seasons starting from November to February. In this study, we identify the extreme cold wave events over north India during the period 1951-2020 and investigate their occurrence with rapid Arctic warming through the Quasi Resonant Amplification (QRA) fingerprint. Our findings reveal that a warm Arctic, double zonal jet formation, and amplification of (baroclinic) wave numbers 6 to 7 were observed during extreme cold waves of north India. The upper tropospheric double jet acts as waveguides, trapping the 6-7 wavenumbers, leading to the amplification of Rossby waves, resulting in the persistence of extreme cold wave conditions. Moreover, the sea ice retreat over the Barents-Kara Sea observed during the extreme cold wave events induced by the Arctic warming weakens the equator-to-pole temperature gradient. This leads to the meandering of the jetstream, and promotes the formation of atmospheric blocks. Consequently, an Omega block emerges over the Ural region leading to the advection of cold air from higher latitudes to the northern parts of the country. Hence our study concludes that the Arctic warming which is confirmed through the QRA fingerprint results in highly persistent and anomalous winter weather conditions in north India.

Key words: Extreme cold wave, Quasi Resonant Amplification, Atmospheric blocking, Arctic warming