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

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: Hunter Brown, Hailong Wang, Mark Flanner, Xiaohong Liu, Balwinder Singh, Rudong Zhang, Yang Yang, Mingxuan Wu
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union (AGU) 2022
• Subjects: aerosol‐snow interactions; brown carbon; SNICAR; climate model; CESM; biomass burning; Physical geography; GB3-5030; Oceanography; GC1-1581; Antarc*; Antarctica
• Online Access: https://doi.org/10.1029/2021MS002768; https://doaj.org/article/b6596f0d771b4098b345dc87c148949b

Abstract 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.