Dasari Sanjeev, Andersson August, Bikkina Srinivas, Holmstrand Henry, Budhavant Krishnakant, Satheesh Sreedharan, Asmi Eija, Kesti Jutta, Backman John, Salam Abdus, Bisht Deewan Singh, Tiwari Suresh, Hameed Zahid, Gustafsson Örjan
Department of Environmental Science and Analytical Chemistry (ACES), Bolin Centre for Climate Research, Stockholm University, Stockholm 10691, Sweden.
Maldives Climate Observatory at Hanimaadhoo (MCOH), Hanimaadhoo, Republic of the Maldives.
Sci Adv. 2019 Jan 30;5(1):eaau8066. doi: 10.1126/sciadv.aau8066. eCollection 2019 Jan.
Light-absorbing organic aerosols, known as brown carbon (BrC), counteract the overall cooling effect of aerosols on Earth's climate. The spatial and temporal dynamics of their light-absorbing properties are poorly constrained and unaccounted for in climate models, because of limited ambient observations. We combine carbon isotope forensics (δC) with measurements of light absorption in a conceptual aging model to constrain the loss of light absorptivity (i.e., bleaching) of water-soluble BrC (WS-BrC) aerosols in one of the world's largest BrC emission regions-South Asia. On this regional scale, we find that atmospheric photochemical oxidation reduces the light absorption of WS-BrC by ~84% during transport over 6000 km in the Indo-Gangetic Plain, with an ambient first-order bleaching rate of 0.20 ± 0.05 day during over-ocean transit across Bay of Bengal to an Indian Ocean receptor site. This study facilitates dynamic parameterization of WS-BrC absorption properties, thereby constraining BrC climate impact over South Asia.
吸光有机气溶胶，即所谓的棕碳（BrC），抵消了气溶胶对地球气候的整体冷却效应。由于环境观测有限，其吸光特性的时空动态在气候模型中受到的限制很大且未得到考虑。我们在一个概念性老化模型中将碳同位素法医鉴定（δC）与光吸收测量相结合，以确定世界上最大的BrC排放区域之一——南亚地区水溶性BrC（WS-BrC）气溶胶吸光性的损失（即漂白）情况。在这个区域尺度上，我们发现大气光化学氧化在印度-恒河平原6000多公里的传输过程中使WS-BrC的光吸收降低了约84%，在经孟加拉湾向印度洋受体站点的越洋传输过程中，其环境一级漂白率为0.20±0.05天⁻¹。这项研究有助于对WS-BrC吸收特性进行动态参数化，从而限制BrC对南亚气候的影响。
