Synoptic changes and contribution of carbonaceous aerosols to spectral absorption coefficient along with radiative forcing in Himalayan region

• Published in: Physics and chemistry of the earth. Parts A/B/C 2024-10, Vol.135, p.103670, Article 103670
• Main Authors: Pipal, Atar S., Panicker, A.S., Kaur, Parminder, Gautam, A.S., Latha, R., Kumar, S., Murthy, B.S.
• Format: Article
• Language: English
• Subjects: BrCprim and BrCsec; Brown carbon; Indian Himalaya region; Radiative forcing; Spectral absorption coefficient
• ISSN: 1474-7065
• DOI: 10.1016/j.pce.2024.103670

The Black carbon (BC) and Brown carbon (BrC) concentration has been measured over Srinagar (Garhwal) in central Himalayas during October 2020 to September 2021 periods. The average BC mass was 2.59 ± 1.96 μg m−3 and its absorption coefficients were abundant at shorter wavelength. BC seasonal variation exhibited a significant variability, with highest during winter (4.54 ± 2.64 μg m−3) followed by pre-monsoon (2.69 ± 2.04 μg m−3) and post-monsoon (1.93 ± 0.91 μg m−3) while lowest was observed in the monsoon (1.05 ± 0.54 μg m−3). Relatively high contribution of total spectral light absorption coefficient (Abs λ) was observed (75.94 Mm−1) at 370 nm than longer wavelength (16.86 Mm−1) at 950 nm. The BrC contribution was higher at 370 nm (32.50 Mm−1) to the total babs (λ), while at higher wavelengths it has extensively decreased (2.54 Mm−1 at 660 nm). Seasonally, the absorption coefficient of BC and BrC was greater in winter (83.99 and 68.37 Mm−1) while lowest in monsoon (19.38 and 9.27 Mm−1), respectively. The babs BrC/babs (t) ratio revealed higher contribution of BrC in winters. The secondary brown carbon (BrCsec) and primary brown carbon (BrCpri) contributed 43.16 % and 56.88 % towards the total BrC Abs (λ) at 370 nm with higher in winter and lowest in monsoon, respectively. BrCsec and BrCprim has shown higher contribution in evening (18.00–20.00 h) and in morning (09.00–11.00 h) hours. The average radiative forcing (RF) of BC was 36.11 ± 6.99 Wm-2, 2.19 ± 1.22 Wm-2 and -33.92 ± 5.96 Wm-2 at the atmosphere (ATM), Top of the Atmosphere (TOA), and at the Surface (SUR), respectively. [Display omitted] •BC and absorption coefficient showed the significant seasonal and diurnal variability.•BrC contribution was higher at 370 nm to the total babs (λ), while at higher wavelengths it has extensively decreased.•Significant higher contribution of BrCsec and BrCpri was at 370 while at higher wavelength it was reduced.•Radiative forcing of BC was found negative at SUR while it was positive in the ATM and TOA.