Lung et al. (2026) The Influence of Open Boundary Conditions and Model Resolution on Shallow Cloud Organization in Atmospheric Large Eddy Simulations

⚠️ Warning: This summary was generated from the abstract only, as the full text was not available.

Identification

• Journal: Journal of Advances in Modeling Earth Systems
• Year: 2026
• Date: 2026-04-01
• Authors: Franciscus Liqui Lung, Christian Jakob, Fredrik Jansson, P.A. Siebesma
• DOI: 10.1029/2025ms005135

Research Groups

Not explicitly stated in the abstract. The study builds upon Savazzi et al. (2023).

Short Summary

This study presents and compares an open boundary, one-way nested high-resolution Large Eddy Simulation (LES) with a periodic LES, both forced by the HARMONIE-AROME regional weather model, to evaluate their representation of cloud structures. It finds that the open boundary LES, by inheriting the full atmospheric state, maintains more constant, larger, and organized clouds compared to the periodic LES, which exhibits stronger daily cycles and intermittent cloud behavior.

Objective

• To compare the representation of cloud structures in a high-resolution Large Eddy Simulation (LES) using an open boundary setup (one-way nested in a low-resolution LES) against a periodic LES, both forced by the HARMONIE-AROME regional weather model.

Study Configuration

• Spatial Scale: High-resolution (high-res) LES nested within a low-resolution (low-res) LES. Cloud structures are refined from larger domains.
• Temporal Scale: Daily cycle of cloudiness is analyzed, implying a multi-day simulation period.

Methodology and Data

• Models used:
  • Large Eddy Simulation (LES) in two configurations:
    • Open boundary, one-way nested high-resolution LES.
    • Periodic LES (from Savazzi et al., 2023).
  • HARMONIE-AROME (regional weather model) used for forcing.
• Data sources:
  • Output from the HARMONIE-AROME regional weather model used as forcing:
    • Domain-averaged tendencies for the periodic LES.
    • Full atmospheric state via boundaries of the low-resolution nested LES for the open boundary setup.

Main Results

• Cloud structures are refined as they transition to higher-resolution simulations, breaking into smaller fragments while retaining their large-scale distribution.
• The high-resolution nested LES produces larger, more organized clouds compared to the periodic LES when cloud fractions are similar.
• The periodic LES exhibits a stronger daily cycle in cloudiness, starting very cloudy and ending with clear skies, leading to deeper, more intermittent clouds and more intense rainfall.
• The periodic LES shows greater variation in cloud structures, from large clouds during cloudy periods to fewer, smaller clouds during low cloud cover.
• In contrast, the high-resolution nested LES maintains more constant cloud cover, with cloud top and size varying more gradually.
• The intermittent behavior of the periodic LES is attributed to the applied horizontally averaged tendencies, which drive the domain toward stable or unstable conditions.
• Inheritance of the full atmospheric state allows the high-resolution nested LES to maintain larger, more organized clouds.

Contributions

• Presents and evaluates an open boundary setup for high-resolution LES, one-way nested in a low-resolution LES, demonstrating its capability to inherit complex atmospheric states.
• Highlights the significant impact of different forcing mechanisms (domain-averaged tendencies vs. full atmospheric state inheritance) on the simulated cloud dynamics and organization in LES.
• Shows that inheriting the full atmospheric state in nested LES leads to more constant, larger, and organized cloud structures compared to periodic LES forced by averaged tendencies.

Funding

Not explicitly stated in the abstract.

Citation

@article{Lung2026Influence,
  author = {Lung, Franciscus Liqui and Jakob, Christian and Jansson, Fredrik and Siebesma, P.A.},
  title = {The Influence of Open Boundary Conditions and Model Resolution on Shallow Cloud Organization in Atmospheric Large Eddy Simulations},
  journal = {Journal of Advances in Modeling Earth Systems},
  year = {2026},
  doi = {10.1029/2025ms005135},
  url = {https://doi.org/10.1029/2025ms005135}
}