Black carbon aerosols over source vs. background region: Atmospheric boundary layer influence, potential source regions, and model comparison

Black carbon (BC) aerosols measured simultaneously over a source (Ahmedabad, urban) and background (Gurushikhar, high-altitude) region are analysed. The influence of atmospheric boundary layer (ABL), potential regions for BC examined, compared with model, the first time. mass in Ahmedabad is significantly higher (2 to 5 times) than Gurushikhar. concentrations peak during morning evening hours when ABL shallow anthropogenic emissions high. In contrast Gurushikhar afternoon due fully evolved upward transport pollutants from valley/foothills winter within ABL. During other seasons diurnal variation suppressed. BCmax close BCmin Ahmedabad, which occurs sources negligible while get transported foothills surrounding Potential contribution function (PSCF) analysis reveals that probable these two locations distinctly different, especially, postmonsoon winter, long range northwestern India Indo-Gangetic Plain (IGP) (agricultural waste biomass burning) high-altitude location. Regional emitted urban areas evident premonsoon PSCF analysis. simulated by 2 models - MERRA-2 (fine resolution) ECHAM6 (coarse underestimated though capture seasonal cycle high monsoon low. simulate well. magnitude both Gurushikar quite similar. This observation-model comparative aerosol emissions, especially its inadequately represented models, particular strongly suggesting improvements emission inventories as well inclusion missing categories needed. Such quantitative evaluation ABL, hitherto unavailable tropics can be used improve representation thereby estimates radiative climate effects aerosols.