Modeling Large Dust Aerosols in the Community Earth System Model Version 2 (CESM2)

Longlei Li, Natalie M. Mahowald, Xiaohong Liu, María Gonçalves Ageitos, Ziming Ke, Danny Leung, Carlos Pérez García-Pando, Ron Miller, Vincenzo Obiso, Paul Ginoux, Jasper Frank Kok, Paola Formenti, Claudia Di Biagio, Phillip G Brodrick, David R. Thompson, Roger N. Clark, Gregory S. Okin, Robert Green, Bo Zhou, Samuel Albani, Adeyemi A Adebiyi 

Dust aerosols have a wide size distribution from less than 1.0 nm to over 100 μm and dominate the Earth’s atmospheric aerosol mass. However, most Earth system models inadequately represent dust aerosols larger than 10 µm in diameter, limiting the accuracy of dust cycle and climatic impact simulations. Here, we introduce a new modeling framework that captures the observed full-size distribution of dust aerosols, incorporating recent advances into a mineral-resolved version of the Community Earth System Model and addressing known issues in previous versions. Comprehensive evaluation against diverse observations of bulk dust and component minerals demonstrates that the model reproduces the observed dust cycle across sizes. Incorporating the previously unrepresented fractions substantially alters dust budget estimates, highlighting potential changes in simulated climatic impacts and underscoring the importance of comprehensive size-resolved dust modeling. Despite these advancements, uncertainties persist. Future developments should address misrepresented physical processes that hinder accurate modeling of the transport of dust aerosols larger than 10 µm in diameter, whose gravitational settling velocity must be reduced by 60% in the new model to match observed size distribution. Expanding observational datasets covering the full-size distribution is also essential to better constrain the dust cycle and improve the representation of dust optical properties and climatic effects.