Regional Aerosol Optical Depth over Antarctica

Abstract

Atmospheric aerosols greatly contribute to the uncertainty in current climate models, particularly presenting pronounced limitations in the Antarctic region. This study measures aerosol properties using data from several Antarctic AERONET sites (Escudero, Marambio, South Pole, Utsteinen, Vechernaya_Hill) and Zhongshan Station. We examined the spatial and temporal patterns of two specific aerosol properties: Aerosol Optical Depth (AOD) at 500 nm (τ500nm) and Ångström Exponent (AE) between 440 and 870 nm (α440−870nm). Our findings reveal τ500nm medians ranging from 0.02 to 0.09, with elevated values observed along the coastal regions compared to the interior of Antarctica. Regarding the AE, the medians of α440−870nm indicate that the coarse-mode particle aerosols are dominated at Escudero (approximately 0.54). In contrast, fine mode particles prevail at the other sites (over 0.97). Monthly mean τ500nm and the proportion of fine mode particles peaks during austral summer and autumn, suggesting increased marine biological sources. Moreover, analyzing the air mass back trajectories, we discovered marine air influences on Escudero, Marambio, Zhongshan, and Vechernaya_Hill, while Utsteinen and South Pole are primarily experiencing air originating from the Antarctic continent. These findings underscore the significant role of aerosol sources in regional AOD differences. Additionally, higher τ500nm were more associated with significantly negative direct aerosol radiative forcing at the bottom of the atmosphere (DARF-BOA). The direct aerosol radiative forcing at the top of the atmosphere (DARF-TOA) closely correlates with single-scattering albedo (SSA), where high (low) SSA generally results in negative (positive) forcing over Antarctica.