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Experiment Summary: Paleoclimate / PMIP (PM)

The Paleoclimate Modelling Intercomparison Project (PMIP or PM) investigates past climate states (e.g. Mid-Holocene, Last Glacial Maximum, Last Interglacial) to understand climate sensitivity and forced Earth System responses outside modern instrumental ranges.

Physical Forcing Rationale & Setup

In paleoclimate simulations where astronomical orbital parameters and ice sheet geometries are modified, modern short-lived atmospheric chemistry must be replaced by a stable, multi-decadal equilibrium climatology:

  • 20-Year Climatological Ozone Mean: Rather than single-year 1850 fields which can exhibit transient anomalies, PMIP utilizes a 20-year climatological mean ozone field averaged over 1850–1870 (ozone_1850_1870_mean_cmip7.anc).
  • Vertical Structure: Zonal-mean 85 hybrid-height levels (L85) on the standard global.N96 atmospheric grid.

Workflow Switches & Selectors

The generation of paleoclimate climatological ozone ancillaries is governed by parameters in rose-suite.conf:

  • Experiment Activation Switch: USE_EXP['PM'] = True
    When set to False, PI_mean_ukesm_ancil_ozone and PI_mean_ancil_ozone are excluded from the Cylc task DAG.
  • Master Forcing Toggle: ANCIL_CREATE_OZONE = true
    Must evaluate to true alongside USE_EXP['PM'] to schedule the climatological ozone pipeline.
  • Climatological Window Parameters:
  • CMIP7_PI_MEAN_OZONE_BEG_YEAR = '1850'
  • CMIP7_PI_MEAN_OZONE_END_YEAR = '1870'
  • Intermediate NetCDF: ${UKESM_PI_MEAN_OZONE_NETCDF_FILENAME} (mmro3_monthly_CMIP7_zonalmn_1850_1870_ants.nc)
  • Final Ancillary: ${ESM_PI_MEAN_OZONE_SAVE_FILENAME} (ozone_1850_1870_mean_cmip7.anc)
  • Reference: See Suite Configuration & Parameters Reference for full object declarations.

Complete Task Roster for Paleoclimate

The following 2 Cylc workflow tasks prepare the climatological ozone ancillary:

Task Name Pipeline Stage Script Entrypoint Primary Input Dataset Output Artifact Technical Specification
PI_mean_ukesm_ancil_ozone Upstream Regrid UKESM ozone toolchain FZJ-CMIP-ozone-2-0 (1850–1870) mmro3_monthly_CMIP7_zonalmn_1850_1870_ants.nc View Card
PI_mean_ancil_ozone UM Ancillary ozone.cmip7_PI_mean_ozone_generate Intermediate NetCDF ozone_1850_1870_mean_cmip7.anc View Card

Downstream Configuration Integration

Artifacts feed into the paleoclimate configuration branches in access-esm1.6-configs:

  • Installation Directory:
    /g/data/${PROJECT}/${USER}/CMIP7/esm1p6_ancil/<ISO_DATE_TODAY>/modern/pre-industrial/atmosphere/forcing/global.N96/<ANCIL_TODAY>/
  • Output Ancillary: ozone_1850_1870_mean_cmip7.anc (12 monthly climatological slices).