Spectral dependence of aerosol light absorption at an urban and a remote site over the Tibetan Plateau

- Aerosol light absorption is measured over the Tibetan Plateau.
- Spectral dependence of aerosol light absorption due to black and brown carbon is studied.
- The absorption Ångström exponent of brown carbon is directly extracted.

We present a study of aerosol light absorption by using a 7-wavelength Aethalometer model AE33 at an urban site (Lhasa) and a remote site (Lulang) in the Tibetan Plateau. Approximately 5 times greater aerosol absorption values were observed at Lhasa (53 ± 46 Mm− 1 at 370 nm and 20 ± 18 Mm− 1 at 950 nm, respectively) in comparison to Lulang (15 ± 19 Mm− 1 at 370 nm and 4 ± 5 Mm− 1 at 950 nm, respectively). Black carbon (BC) was the dominant light absorbing aerosol component at all wavelengths. The brown carbon (BrC) absorption at 370 nm is 32 ± 15% of the total aerosol absorption at Lulang, whereas it is 8 ± 6% at Lhasa. Higher value of absorption Ångström exponent (AAE, 370-950 nm) was obtained for Lulang (1.18) than that for Lhasa (1.04) due to the presence of BrC. The AAEs (370-950 nm) of BrC were directly extracted at Lulang (3.8) and Lhasa (3.3). The loading compensation parameters (k) increased with wavelengths for both sites, and lower values were obtained at Lulang than those observed at Lhasa for all wavelengths. This study underlines the relatively high percentage of BrC absorption contribution in remote area compared to urban site over the Tibetan Plateau.

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