Session 7: Perturbation Experiments in ACCESS-OM2 / Multiple Sensitivity Tests using Experiment Generator & Runner

COSIMA 2025 training program
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ACCESS-OM2 Perturbation Experiments – Meeting Notes

Intro

  • Thanks for attending
  • Overview of ACCESS-OM facilities
  • Minghang: new improvements for perturbation experiments

Why Perturbations?

  • Experiments with meltwater, Antarctica, air temperature
  • Study climate change impacts on ocean
  • Storms near poles / extreme events
  • Useful for engineering fixes

ACCESS-OM2 Architecture

  • Forcing data → model
  • JSON config (array of dictionaries)
    • Keys/values: e.g., zonal wind, year
    • Field names = NetCDF variables

Perturbation Approaches

  • Manual (hard)
    • Copy + modify NetCDF files
    • Edit forcing.json
    • Downsides: poor provenance, messy ensembles
  • Online (preferred)
    • Perturbations calculated at runtime
    • Easy ensemble management

Implementation

  • Define data in JSON
  • Must match original spatial/temporal dimensions
  • Supports:
    • Multiple scalings & offsets
    • Temporal ramps
    • Reduced dimensions (1D × 2D → 3D)
  • EOF components & calendar alignment

Minghang Workflow

  • Run physical simulations from GitHub directory
  • Scaling: time-independent 2D / uniform increases
  • Archive / restart management via payu
  • YAML + git handles:
    • Branch creation per perturbation
    • Job submission & tracking
  • Payu ensures reproducibility & retries failed runs

Resources

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