Accounting for aerosol behavior and air pollution in the Indian context needs a paradigm shift

Please join us for our CEMPD Seminar at 9 a.m. on Jan. 17 in CSQ 3002 with Zainab Arub of Indian Institute of Technology, Mumbai, India.

We are facing today an age where climate change and air pollution have become global concerns. Addressing these challenges involves modelling aerosol behaviour to determine their impacts on climate, conforming to observation datasets, and developing clean air initiatives for air pollution mitigation. These are currently largely shaped by the understanding of the West that has preceded developing countries in undertaking these efforts. However, with the deepening realization of the seriousness of these issues, countries like India have also come forward to take initiatives to address climate change and air pollution. Consequently, this work focuses on the nuances in the understanding of how aerosol physio-chemical properties impact hygroscopicity parameter (κ) and cloud condensation nuclei (CCN) formation, and the impact of mineral dust on aerosol hygroscopicity based on observations for New Delhi. The paradigm shift in this context comes from a very low critical diameter (25–130 nm, for 0.1- 0.8 % SS) for Delhi, the world’s highest activated fraction (0.71±0.14 at 0.4 % SS) for a continental site, and the huge underestimation of κ for a polluted site subject to heavy mineral dust loading (~ 60% for both day and night) if only ammonium salts are assumed to be dominant. From a policy perspective, India’s National Clean Air Program (NCAP) is city-centric and focused on mitigation measures in the transport and industry sectors. In this case, the paradigm shift is driven by developing a regionally representative emission inventory (PAVITRA 2019) to model NCAP policies in the highest detail using a reduced complexity model (India-InMap). PM2.5 levels across non-attainment cities are driven heavily by positive externalities and reliance on non-urban interventions focused on residential and agriculture sectors to accomplish NCAP goals. Policy interventions at non-urban scales are key to large air quality gains at multiple spatial scales. These findings open a window to better quantify aerosol direct and indirect effects, precipitation predictions by Global Climate Models (GCMs), and inform air pollution policies to deliver clean air to everyone.