AIDA Arctic transport experiment (part 1): simulation of northward transport and aging effect on fundamental black carbon properties

Abstract. Black carbon (BC) is a key atmospheric forcer due to its interaction with solar radiation and clouds. However, accurately quantifying and understanding the impact of atmospheric aging on BC properties and radiative forcing remains a major challenge. To address this, the AIDA aRCtic Transport Experiment (ARCTEx) project simulated BC aging under quasi-realistic Arctic conditions in the AIDA (Atmospheric Interactions and Dynamics in the Atmosphere) chamber. Four distinct scenarios were simulated based on reanalysis data, representing summer and winter conditions at both low and high altitudes, to capture the variability in BC aging processes during Arctic transport.

In the first part of the paper, we define the meteorological conditions characterizing norward transport under different scenarios and describe the technical solutions to simulate 5-day transport in the AIDA chamber. In the second part of the work, we assess the evolution of fundamental properties including density, morphology and mixing state observed during the aging process.

The ARCTEx project demonstrates that large facilities such as AIDA can successfully reproduce environmental conditions, enabling a gradual aging process that closely follows the natural timescales observed in the atmosphere. Our experiments revealed that temperature strongly influences the aging timescale and the evolution of BC’s diameter, effective density and coating thickness. Low-altitude scenarios exhibited rapid aging, resulting in fully-coated, compact BC particles within 39 – 98 hours, corresponding to 50° N and 80° N respectively. In contrast, high-altitude transport was characterized by slow aging, with limited coating and compaction, even after 115 hours of simulation. These findings provide valuable insights into the temporal evolution of BC properties during Arctic transport. In forthcoming work, we will report the implications of this evolution on climate-relevant properties such as light absorption and activation as cloud droplets and ice crystals. Together, these studies aim to enhance the representation of BC aging in climate models, reducing uncertainties in Arctic radiative forcing estimates.