Measurement report: Contrasting elevation-dependent light absorption by black and brown carbon: lessons from in situ measurements from the highly polluted Sichuan Basin to the pristine Tibetan Plateau

Abstract. Scientific knowledge about light absorption by aerosols is extremely limited at the eastern slope of Tibetan Plateau (ESTP). We conducted first aerosol field experiment six sites (Chengdu, Sanbacun, Wenchuan, Lixian, Maerkang, Hongyuan) along ESTP, ranging in elevation from 500 to 3500 m. The fraction brown carbon (BrC) total increases 20 % 50 with altitude, and mass efficiency (MAE) BrC over (TP) 2–3 times higher than that inside Sichuan Basin (SCB), especially winter. In contrast, MAE elemental (EC) winter decreases altitude. contrasting variation EC altitude mainly attributed source differences between TP SCB. Emissions more urban sources (motor vehicles, industries, etc.) SCB fail be transported due stable air basin, which also favourable for ageing enhance efficiency. radiative forcing relative varies 0.10 0.42 as organic (OC) ratio Thus, reason enhanced polluted pristine concentration slowly This study contributes understanding difference lower-altitude basins TP, provides a data set regional climate model validation.