UCLA

Abstract Dust aerosols have a wide size distribution from less than 0.1 to over 100 μm and dominate Earth's atmospheric aerosol mass. However, most Earth system models (ESMs) inadequately represent dust aerosols larger than 10 μm in diameter, limiting the accuracy of the simulated dust cycle and climate impacts. Here, we introduce a new modeling framework that captures the full observed size distribution of dust aerosols, incorporating recent advances into a mineral‐resolved version of the Community ESM, while 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 particle sizes. Incorporating the previously unrepresented large‐dust fractions substantially alters dust budget estimates, highlighting potential changes in simulated climate impacts and underscoring the importance of comprehensive size‐resolved dust modeling. Despite these advancements, uncertainties persist. Our results indicate that a size‐dependent reduction in settling velocity is required to reproduce the observed dust size distribution downwind of source regions. Specifically, in the new model, the gravitational settling velocity of dust particles larger than 10 μm in diameter must be reduced by as much as 85% to achieve agreement with observations. This empirical reduction serves as a constraint on physics‐based models of dust settling. Future developments should address misrepresented physical processes that hinder accurate modeling of the large dust aerosol transport. Expanding observational data sets covering the full‐size distribution is also essential to better constrain the dust cycle and improve the representation of dust optical properties and climate effects. Plain Language Summary Mineral dust constitutes the largest mass of airborne particles on Earth. These particles span a wide range of sizes from tiny to giant, but not all sizes play an equally important role. As particles that both scatter and absorb solar and thermal radiation while delivering vital nutrients to ecosystems, mineral dust plays a critical role in various Earth system processes and in projections of future climate changes. However, most Earth system models (ESMs), including the Community ESM version 2 (CESM2), either neglect or underrepresent particles large than 10 microns in diameter, limiting our understanding of dust's full influence on climate. Furthermore, the CESM2 dust module, including its mineral‐resolved version used in this study, lacks several key physical processes known to affect dust emission and transport. This study enhances the representation of dust aerosols in the mineral‐resolved version of CESM2 by extending the upper size limit of simulated dust particles to 70 microns at emission and adding omitted physical processes for dust emission based on the latest scientific findings. The updated model is evaluated against a wide range of observations under present‐day climate conditions. Key Points A new model is developed to simulate dust aerosols for a wide distribution of sizes with observational constraints and improved mineralogy Including particles larger than 10 microns in diameter greatly alters simulated dust budgets while not degrading finer dust representation Challenges remain, especially for representing the physical mechanisms that transport super‐coarse and giant dust in Earth system models