Modulation of temporal evolution of black carbon aerosols at a rural location in the Western Ghats by meteorology and boundary layer dynamics

Black carbon (BC) aerosols have been reported to influence the precipitation patterns over South-East Asia. In this study, we present surface measurements of BC carried out from a rural location in the Western Ghats and covering all the seasons. Despite being a remote location with negligible anthropogenic emissions, the total BC concentration is strongly modulated by particles originating from fossil fuel burning (~75%). Contrary to the prominent role played by boundary layer dynamics in the diurnal variations of BC in the tropics, our measurements reveal a disconnection between boundary layer dynamics and BC concentration mostly due to the advection from a distant urban location being the dominant source of BC. However, this influence is conspicuous on the concentration of particles originating from biomass burning. Seasonal variations in the wind fields, surface temperature, and rainfall are observed to influence the BC concentration, thereby leading to distinct diurnal variations seldom reported elsewhere. Reanalysis data sets fail to capture these changing patterns in BC, with daily mean concentrations exhibiting large differences with our observations (particularly in winter months) and diurnal patterns being different throughout the season. Under this backdrop, incorporation of these measurements could possibly improve the monsoon forecast in global climate models and provide deeper insights on the role of meteorology and boundary layer dynamics on aerosol fields in complex environments.