Carbonaceous aerosols, an ubiquitous component of Earths atmosphere, contribute ~20-70% of total aerosol mass over urban regions and affect radiation budget, hydrological cycle and climate on a regional to global scale both via direct and indirect effects. The formation of secondary aerosols, in conjunction with the airborne particles of primary origin, has been recently recognized as a dominant process contributing to air pollution over urban areas. In addition, secondary aerosols are more hygroscopic and play an important role in the modification of the cloud activation processes by acting...