Preprints
https://doi.org/10.5194/egusphere-2025-4351
https://doi.org/10.5194/egusphere-2025-4351
01 Oct 2025
 | 01 Oct 2025
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Idealized Particle-Resolved Large-Eddy Simulations to Evaluate the Impact of Emissions Spatial Heterogeneity on CCN Activity

Samuel G. Frederick, Matin Mohebalhojeh, Jeffrey H. Curtis, Matthew West, and Nicole Riemer

Abstract. Aerosol-cloud interactions remain a large source of uncertainty in global climate models (GCMs) due to complex, nonlinear processes that alter aerosol properties and the inability to represent the full compositional complexity of aerosol populations within large-scale modeling frameworks. The spatial resolution of GCMs is often coarser than the scale of the spatially varying emissions in the modeled geographic region. This results in diffuse, uniform concentration fields of primary aerosol and gas-phase species instead of spatially heterogeneous concentrations. Aerosol processes such as gas-particle partitioning and coagulation are concentration-dependent in a non-linear manner, and thus the representation of spatially heterogeneous emissions impacts aerosol aging and properties. This includes climate-relevant quantities key to aerosol-cloud interactions including particle hygroscopicity and cloud condensation nuclei (CCN) activity. We investigate the impact of emissions spatial heterogeneity on aerosol properties including CCN activity via a series of first-of-a-kind particle-resolved large-eddy simulations with the modeling framework WRF-PartMC-MOSAIC-LES. CCN concentrations within the planetary boundary layer (PBL) are compared across numerous scenarios ranging in emissions spatial heterogeneity. CCN concentrations at low supersaturations (Senv = 0.1–0.3 %) increase in the upper PBL by up to 25 % for emissions scenarios with high spatial heterogeneity when compared to a uniform emissions base case. Process level analysis indicates that this increase is due to enhanced nitrate formation among scenarios with high emissions spatial heterogeneity.

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Samuel G. Frederick, Matin Mohebalhojeh, Jeffrey H. Curtis, Matthew West, and Nicole Riemer

Status: open (until 12 Nov 2025)

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Samuel G. Frederick, Matin Mohebalhojeh, Jeffrey H. Curtis, Matthew West, and Nicole Riemer

Data sets

Data for "Idealized Particle-Resolved Large-Eddy Simulations to Evaluate the Impact of Emissions Spatial Heterogeneity on CCN Activity" Samuel Frederick et al. https://doi.org/10.13012/B2IDB-9622921_V2

Model code and software

WRF-PartMC-MOSAIC-LES Samuel Frederick et al. https://doi.org/10.5281/zenodo.16850290

Interactive computing environment

Data for "Idealized Particle-Resolved Large-Eddy Simulations to Evaluate the Impact of Emissions Spatial Heterogeneity on CCN Activity" Samuel Frederick et al. https://doi.org/10.13012/B2IDB-9622921_V2

Samuel G. Frederick, Matin Mohebalhojeh, Jeffrey H. Curtis, Matthew West, and Nicole Riemer

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Short summary
We show with detailed computer simulations that spatial patterns of emissions strongly affect aerosols and their ability to seed clouds. Highly variable emissions can raise cloud-forming particle concentrations in the boundary layer by up to 25 %. Because clouds regulate climate and precipitation, these findings underscore the need to represent realistic emission patterns to improve climate predictions.
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