Centre for Science and Environment Analysis 1 Decoding winter air pollution in cities of Southern India Anumita Roychowdhury and Avikal Somvanshi Centre for Science and Environment, New Delhi, January, 2021 This analysis is part of the next in the series of air quality tracker initiative the Centre for Science and Environment (CSE) to follow changing patterns of air quality trends in different regions of the country. This seeks to understand the impact of the extraordinary year 2020 that has witnessed one of the biggest disruptions in the recent times. This is also an inflexion point at the onset of the new decade. This addresses basic curiosities around the impact of the lockdown, lowering of the regional influence on local air quality, and deeper seasonal patterns that unmask the underlying high trends despite the lockdown phases. After analyzing the changing trends in the Indo-Gangetic Plain, Delhi and National Capital region, Rajasthan, Maharashtra, and West Bengal, this analysis unravels the pattern in cities of Southern India– vulnerable but poorly monitored region from air quality perspective. New analysis of winter pollution (until 26 January of this year), shows how clean air gains of the lockdown and monsoon period were lost with the reopening of the economy and with the onset of the winter. Even though the atmospheric conditions during winter in this region is not the same as that of the Indo Gangetic Plain in the northern region, trapping of winter pollution is not insignificant either -- especially in inland cities. Higher PM 2.5 levels is a typical and predictable winter trend when continuous emissions from local sources including vehicles, industry, construction, and episodic pollution from biomass burning get trapped due to meteorological changes. But winter is not as harsh in southern cities therefore impact of inversion is expected to be limited, yet pollution build-up has been noted. Even though the average level of PM 2.5 for the summer and monsoon months in 2020 is considerably lower than the previous year due to the pandemic related to summer lockdown, the PM 2.5 levels this winter have risen beyond the 2019 in most of the monitored cities. Chennai and Thiruvananthapuram being the only exception. Combination of the reopening of the economy and changing meteorology is responsible for high winter pollution but this regional variation calls out for more nuanced and robust pollution control strategy. The region cannot rely only on natural advantage of warmer winters and sea breeze to avoid bad air. This demands speed and scale of action. This detailed data analysis points to the fact that the air pollution is a south India problem as well and this requires quicker reforms and action in key sectors of pollution – vehicles, industry, power plants and waste management to control winter pollution and further bend the annual air pollution curve. Data used in the analysis: The analysis is based on publicly available granular real time data (15-minute averages) from the Central Pollution Control Board’s (CPCB) official online portal Central Control Room for Air Quality Management. Real-time data from 36 cities was accessed but only 21 cities – Hyderabad, Amaravati, Rajamahendravaram, Tirupati, Visakhapatnam, Bagalkot, Chikkaballapur, Chikkamagaluru, Hubballi, Mysuru, Ramnagara, Vijaypura, Yadgir, Bengaluru, Coimbatore, Chennai, Kannur, Kollam, Kozhikode, Kochi, and Thiruvananthapuram have been selected for this analysis because real time data is available for these cities for whole of 2020. This has analysed data recorded by 10 air quality monitoring stations at Bengaluru, 8 stations in Chennai, 6 stations in Hyderabad, 3 stations in Kochi, 2 stations in Thiruvananthapuram, one station each rest of the cities under the Continuous Ambient Air Quality Monitoring System (CAAQMS) of CPCB. Weather data for Bengaluru, Chennai, Hyderabad, Thiruvananthapuram, and Visakhapatnam has been sourced from the weather stations of Indian Meteorological Department (IMD) located at the airport of each city. This air quality trend analysis does not include investigation of local sources of pollution. Key highlights