Night-time showers may keep Deepavali pollution in check

CHENNAI: With the northeast monsoon turning active over Tamil Nadu and a fresh low-pressure system brewing over the southeast Arabian Sea, Chennai is poised to receive multiple spells of rain, particularly during the night and early morning hours, just when Deepavali firecracker activity peaks. While the bursting of crackers generally leads to a sharp spike in PM2.5 and nitrogen oxide levels, meteorologists say the prevailing weather conditions may help suppress pollution buildup this festive week. According to the Regional Meteorological Centre, Chennai is likely to receive moderate rain with thunder and lightning, especially between midnight and early morning, a classic pull-effect rain pattern triggered by the strengthening circulation over the Comorin Sea. Moisture-laden winds along the coast, combined with a developing system in the Arabian Sea, will ensure frequent rain spells over Chennai. This is likely to keep air quality from deteriorating, a met official said. Typically, pollution levels spike on the night of Deepavali due within a concentrated window -- 6 am to 7 am and 7 pm to 8 pm -- as per Supreme Court guidelines. However, rain-induced wet deposition, where pollutants settle faster due to moisture in the air, can limit particulate matter accumulation. Last year, Besant Nagar, T Nagar, Nungambakkam and Valasaravakkam recorded poor air quality index, while Triplicane, Sowcarpet and Tiruvottiyur recorded moderate air quality. Beyond Chennai, heavy rains have been are forecast in Nilgiris, Coimbatore, Theni, Virudhunagar, Ramanathapuram, Thoothukudi, Kanniyakumari and Tirunelveli on Deepavali day. Dindigul and Tiruppur are set to see intense spells over the weekend. This active rainfall spell will continue for next one week. Tamil Nadu Pollution Control Board has urged residents to opt for green crackers and community celebrations. TNPCB will monitor air quality in real time across major urban centres, including Chennai, Coimbatore, Madurai and Trichy.