| Abstract : | In this era of rapid urbanisation and industrialisation, large dependence on carbon-based fuel has led to a substantial increase in the concentrations of carbonaceous aerosols (organic carbon-OC and black carbon-BC) which are emitted from their incomplete combustion. These aerosols are important due to their direct adverse effects on health, radiation budget and their indirect effect in altering cloud properties, thus acting as strong short term climate forcers. However, assessment of the overall impact of these aerosols is a challenging task because of the large spatial and temporal variations, types of mixing states and dynamic atmospheric processes. Despite the scientific attention on this, systematic and high-resolution observations of carbonaceous aerosols are still very limited in South Asia. Such measurements are almost inexistent in the Himalayan region, which has a complex topography and lies in close proximity to polluted regions like the Indo-Gangetic Plain (IGP).
Underlying the aforesaid issues, I will present in this talk, my PhD thesis work from the long term online and offline observations of OC, BC, CO, TSPM along with absorption cross-section from a high-altitude location in the Central Himalayas (ARIES, Nainital). I will first introduce carbonaceous aerosols, the challenges in their study and the importance of this work to overcome these challenges. Later, I will explain the in situ instruments, satellites and models used in the work for their characterisation. Then I will chapter wise present the results, discussing about their temporal variations, factors governing their diurnal and seasonal concentrations, importance of site, wavelength and month specific mass absorption cross-section estimated for the first time over the region, quantification of the sources of these aerosols over this region, novel methods employed for their source characterisation, impact of fossil fuel and biomass emissions, impact of long range transport, the underlying concentration trend and their impact on regional radiative forcing.
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