Impacts of current and climate induced changes in atmospheric stagnation on Indian surface PM2.5 pollution
Mi Zhou, Yuanyu Xie, Chenggong Wang, Lu Shen, Denise L. Mauzerall
Abstract
Severe PM2.5 pollution threatens public health in India. Atmospheric stagnation traps emitted pollutants, worsening their health impacts. Global warming is anticipated to alter future stagnation patterns, impacting the effectiveness of air quality policies. Here, we develop a region-specific index that characterizes meteorological conditions driving stagnation and associated PM2.5 increases. Applying this index to an ensemble of climate models and global warming scenarios, we find that future stagnation changes result from both global CO2-driven circulation changes and local aerosol-driven meteorological responses. By 2100, we project an increase in winter stagnation in the Indo-Gangetic Plain (IGP) of 7 ± 3 days that leads to an increase in PM2.5 of ~7 ug/m3 in a high-warming and high-aerosol scenario. However, annual stagnation occurrences decrease across most of India. Thus, stringent air quality regulations in the IGP during winters will be critical to reduce surface PM2.5 concentrations as climate warms. Such regulations will directly improve air quality while reducing future stagnation occurrences, providing additional air quality benefits. Atmospheric stagnation worsens PM2.5 pollution over India. This study develops a new index that projects ~7 more winter stagnation days over the IGP by 2100. Stringent enforcement of air pollution regulations will be critical to reduce health impacts.