Brown Carbon Fuel and Emission Source Attributions to Global Snow Darkening Effect

• Published in: Animals
• Main Authors: Brown, Hunter, Wang, Hailong, Flanner, Mark, Liu, Xiaohong, Singh, Balwinder, Zhang, Rudong, Yang, Yang, Wu, Mingxuan
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Cambridge University Press 2022
• Subjects: aerosol-snow interactions; brown carbon; climate model; CESM; biomass burning; SNICAR; Geological Sciences; Science; Annals of Glaciology; Antarc*; Antarctica; Arctic
• Online Access: https://hdl.handle.net/2027.42/172343; https://doi.org/10.1029/2021MS002768

Snow and ice albedo reduction due to deposition of absorbing particles (snow darkening effect [SDE]) warms the Earth system and is largely attributed to black carbon (BC) and dust. Absorbing organic aerosol (BrC) also contributes to SDE but has received less attention due to uncertainty and challenges in model representation. This work incorporates the SDE of absorbing organic aerosol (BrC) from biomass burning and biofuel sources into the Snow Ice and Aerosol Radiative (SNICAR) model within a variant of the Community Earth System Model. Additionally, 12 different emission regions of BrC and BC from biomass burning and biofuel sources are tagged to quantify the relative contribution to global and regional SDE. BrC global SDE (0.021–0.056 Wm−2 over land area and 0.0061–0.016 Wm−2 over global area) is larger than other model estimates, corresponding to 37%–98% of the SDE from BC. When compared to observations, BrC simulations have a range in median bias (−2.5% to +21%), with better agreement in the simulations that include BrC photochemical bleaching. The largest relative contributions to global BrC SDE are traced to Northern Asia (23%–31%), Southeast Asia (16%–21%), and South Africa (13%–17%). Transport from Southeast Asia contributes nearly half of the regional BrC SDE in Antarctica (0.084–0.3 Wm−2), which is the largest regional input to global BrC SDE. Lower latitude BrC SDE is correlated with snowmelt, in-snow BrC concentrations, and snow cover fraction, while polar BrC SDE is correlated with surface insolation and snowmelt. This indicates the importance of in-snow processes and snow feedbacks on modeled BrC SDE.Plain Language SummaryBright surfaces like snow and ice reflect some of the sun’s light back to space, leading to less surface warming. These reflective surfaces can be coated by light absorbing particles such as soot and dust, reducing their reflectivity and speeding up the warming of the climate. “Brown carbon” is another absorbing particle that also darkens these surfaces. Fewer studies have looked ...