Meeting Minutes 2026: Atmosphere Working Group

Atmosphere Working Group
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Minutes: Atmosphere Working Group 27 May 2026

19 participants on Zoom

Updates:
Paul: Regional Coupled model is progressing - currently have a box, and coupling between atmosphere in ocean is working

Julie: Reminder about CMIP 7 Analysis Planning Meeting on Friday: Australian CMIP7 analysis meeting: 11am-1pm Friday 29 May (online)

Talk: Highlights from the past year of 21st Century Weather’s regional modelling activities (Bethan White)

  1. Diabatic Processes in tropical-extra tropical interactions (led by Corey Robinson)
    Modified value of the latent heat of vaporisation in ACCESS rAM3 simulations
    Finding: Weakened latent heating → weaker cyclone develops
    Strengthened latent heating → stronger cyclone develops

  2. Roles of Moisture and moisture gradient in moisture modes (led by Reyhan Resparti)
    Case study, with smoothed or steeper moisture gradient
    Finding: Weakened moisture gradient → strength of precipitation and cyclone weaken
    Strengthened moisture gradient → stronger TC and more precipitation
    Same experiments at 12km and 4km (convection permitting) configs - structures different, but same results apply.

  3. Semi-idealised simulations on extratropical TC transitions (led by Chenhui Jin)
    Idealised perturbations into ICs and BCs of ACCESS rAM3.
    Standard ACCESS rAM3 setup, with idealised perturbation for idealised vortex added into the ICs.
    Finding: The perturbations result in downstream Rossby wave amplification

  4. Role of Diabatic processes in an explosive cyclone
    PV tracers. Contributions to the total PV by each of the parametrisation in the model (eg latent heating from convection and microphysics).

  5. Km-scale modelling for sub-hourly extreme precipitation (led by Leena Khadke)
    Case study of extreme precipitation in Melbourne 29 December 2016. Compared access rAM3 1.1km, 4.4km, BARRAC2 and Radar.
    Finding: The model appears to reduce precipitation bias at short duration

  6. Mid-level vortex maintenance (led by Michael Barnes)
    ACCESS rAM3 12km. Calculated PV tendencies from difference parametrisation schemes.
    Finding: Microphysics and diabatic processes dominate mid-level PV production.

  • Many other activities going on
  • People are engaging with the model code and modifying the model
  • Many developments going on, eg ACCESS-rAM3.

Talk: Development of a global high resolution version of ACCESS AM3 (Julie Arblaster)

Alpha-release of ACCESS AM3 global with Cable (Australian land-surface model) + NOAA OISST.
Goal: 25 km resolution.
Many issues have been solved (problematic values in ancillary files, incorrect settings in ozone fields, bugs in CABLE, unrealistic THETA values in ICs etc.)
Control 1 Jan - 31 Dec 2008 N512 (~same ancils as N96)
Land experiments with urban model
Update SSTs to higher resolution (noted also differences in spatial patterns).
Cloud feedbacks, aerosols
!! We want everyone’s help to look at these test experiments !!
Tests will feed into BETA release next month.

Planning experiments with BETA release:

  • What’s the impact of resolution on weather in El Niño versus La Niña years?
  • Daily rather than monthly SSTs
  • Avoid issues of spin-up with the land-surface
  • 3-year sequences of El Niño, Neutral and La Niña X 5 ensemble members
  • Hope to submit to HighResMIP2 - 1980-2022 high-res SST 7MSU plus disk space
  • Also working towards High-res CM3.

Discussion:

  • Time varying aerosols in N512? Probably not necessary in ENSO experiments. Might be an issue to HighResMIP experiments.

  • Are there indications that the high-resolution is better? Indication that N512 is doing better at extreme rainfall, but we still need to look more at weather systems.

Other updates:

ACCESS community workshops - split into 3 smaller workshops.

  • Compute - we still have 2MSU left.