Pardo et al. (2025) Dynamics of Downdrafts Around a Growing Convective Cloud: A Numerical Study

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

Identification

• Journal: Journal of Geophysical Research Atmospheres
• Year: 2025
• Date: 2025-11-11
• Authors: Lianet Hernández Pardo, Hugh Morrison, Anna Possner
• DOI: 10.1029/2025jd044236

Research Groups

Not available from the provided abstract.

Short Summary

This study investigates the dynamics of cloud-edge downdrafts in growing isolated cumuli, revealing that the most intense downdrafts are predominantly driven by dynamic pressure accelerations rather than buoyancy, and are stronger than predicted by simple vortex models.

Objective

• To examine the dynamics of cloud-edge downdrafts over the growth phase of isolated cumulus clouds using Eulerian and Lagrangian analyses.

Study Configuration

• Spatial Scale: Cloud-scale (tens of meters to a few kilometers), focusing on circulations within a radius of approximately twice the updraft radius.
• Temporal Scale: Tens of minutes to hours, covering the entire growth phase of isolated cumulus clouds.

Methodology and Data

• Models used: Numerical simulations (quasi-laminar setups forced by a warm bubble and turbulent setups forced by surface fluxes).
• Data sources: Numerical simulation data, analyzed using Eulerian and Lagrangian vertical momentum budget analyses.

Main Results

• Growing cumuli are consistently surrounded by downdrafts linked to cloud-scale quasi-toroidal circulations at middle and upper cloud levels.
• These toroidal circulations are responsible for the most intense cloud-edge downdrafts observed in the simulations.
• In the upper cloud half, the upward mass flux compensation fraction within a radius of approximately twice the updraft radius is typically 30%–50% in quasi-laminar simulations and 10%–30% in turbulent simulations.
• The most intense cloud-edge downdrafts, particularly in turbulent setups and after spin-up in quasi-laminar experiments, are predominantly mechanically forced by dynamic pressure accelerations, rather than buoyancy.
• This mechanical forcing mechanism is consistent throughout the cumulus growth phase and across varying environmental assumptions (drier and moister conditions).
• The downdraft speed (relative to the corresponding updraft velocity) exceeds the prediction of the non-buoyant Hill's spherical vortex model by more than 30%.

Contributions

• Challenges the traditional buoyancy-centered view of subsiding shells around convective clouds by demonstrating that dynamic pressure accelerations are the primary drivers of intense cloud-edge downdrafts.
• Provides quantitative estimates of upward mass flux compensation fractions for different cloud simulation setups (quasi-laminar vs. turbulent).
• Reveals that cloud-edge downdraft speeds are significantly stronger than predicted by commonly used simple analytical models like Hill's spherical vortex.
• Offers a comprehensive analysis combining Eulerian and Lagrangian perspectives to elucidate the forcing mechanisms of cloud-edge downdrafts.

Funding

Not available from the provided abstract.

Citation

@article{Pardo2025Dynamics,
  author = {Pardo, Lianet Hernández and Morrison, Hugh and Possner, Anna},
  title = {Dynamics of Downdrafts Around a Growing Convective Cloud: A Numerical Study},
  journal = {Journal of Geophysical Research Atmospheres},
  year = {2025},
  doi = {10.1029/2025jd044236},
  url = {https://doi.org/10.1029/2025jd044236}
}