About 70% of the year-to-year variation in winter air pollution across northern India may be explained by the frequency of western disturbances, possibly providing warning of unusually polluted winter months in advance, researchers said.
Western disturbances are storm systems that travel eastwards from the Mediterranean region towards South Asia by strengthening vertical ventilation and bringing precipitation that helps clear accumulated pollution, including PM2.5, from the air. Air pollution levels across northern India, including Delhi-NCR, spike during the winter season, increasing residents’ health risks. A combination of vehicle emissions, stubble burning in the neighbouring states of Punjab, Haryana and Uttar Pradesh and weather patterns that trap pollutants close to the ground is attributed to the seasonal spike in pollution. Emergency measures, including pausing construction, restricting industries and limiting traffic, are implemented on severe pollution days, but may be a challenge if put in place on short notice.
The team said winters with more frequent western disturbances tend to experience lower air pollution levels, while winters with fewer of these storms are more susceptible to persistent severe pollution. “Currently, many of the most disruptive air-pollution measures are taken only after severe pollution is already developing,” lead author Yuanyu Xie, an associate research scholar at Princeton University’s School of Public and International Affairs, U.S., said. “If scientists can anticipate the overall severity of the coming winter months ahead of time, governments, businesses, and communities will have more time to prepare,” Ms. Xie said. The team said the overall severity of winter pollution in north India may thus be predicted about a season in advance.
