Quantifying Size-Resolved Dust Concentrations in the Mixed-Phase Cloud Regime

Mixed-phase clouds (MPC) are an important fixture of the climate system and play a key role in regulating the Earth’s energy balance. The partitioning of ice crystals among liquid droplets in MPCs controls their interactions with radiation. This glaciation state is highly sensitive to the concentration of ice-nucleating particles (INPs), which is significantly impacted by the amount of dust. This is because dust particles are particularly effective at nucleating ice, especially at temperatures colder than approximately -15°C. Therefore, in order to improve climate models, it is critical that dust concentrations are accurately represented to account for their impact on the abundance and properties of MPCs.

In this study, we evaluated to what extent models can correctly represent size-resolved dust concentrations in the MPC regime by focusing on two temperature ranges: low (-37°C to -20°C) and high (-20°C to 0°C). Our analysis compared size-resolved dust concentration observations from the Atmospheric Tomography Mission (ATom) against simulated concentrations from DustCOMM, a dust reanalysis product, and five global climate models. We found that both the models and DustCOMM consistently predict higher dust concentrations than observed at finer dust diameters, suggesting that fine dust emissions may be overestimated or that removal processes are more efficient for coarser dust particles. Moving forward, we aim to develop a dust climatology utilizing DustCOMM that can be integrated into climate models which will produce more accurate results with low computational costs. This will improve our understanding of how dust influences the glaciation state of MPCs and potentially provide more insight into the possibility of using MPC seeding as climate intervention.