Over the last more than four decades, extensive and comprehensive research has been carried out on the primary emissions of atmospheric aerosols and their impact on Earth’s radiation budget, weather, and climate in India, but the secondary source of aerosols (via gas-to-particle formation of new particles and their growth) has largely been unexplored in the Indian context, particularly the chemical process-level understanding of their formation and evolution in the atmosphere.

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While the new particle formation was reported as early as the 1960s in the USA, Europe, and other countries, it was reported in India in 2005. Thus, secondary aerosol formation and growth have received growing attention in recent decades, with their implications for air quality, human health, weather, and climate. Further, aerosol-cloud interaction is still the least understood process in the climate system, partly due to ambiguity in cloud condensation nuclei (CCN) production, which itself stems from uncertainties in the CCN formation from primary and secondary aerosol formation processes.