AntPAMIP-400: harmonized member-resolved atmospheric diagnostics from Antarctic sea-ice–SST perturbation large ensembles

AntPAMIP-400 is a harmonized, member-resolved atmospheric dataset derived from Polar Amplification Model Intercomparison Project (PAMIP) atmosphere-only simulations. It contains 400 independent ensemble members from HadGEM3-GC31-MM and IPSL-CM6A-LR, comprising 100 pdSST-pdSIC control members and 100 pdSST-futAntSIC members for each model. The pdSST-futAntSIC experiment represents a combined Antarctic sea-ice–sea-surface-temperature lower-boundary perturbation and should not be interpreted as a sea-ice-only intervention. Control and treatment members are independent ensembles; matching variant labels do not establish paired initial-condition realizations. The release includes member-resolved native-grid air temperature, zonal wind, meridional wind and geopotential-height fields; NDJFM seasonal-zonal products on a common latitude grid; transient-eddy heat, kinetic-energy and momentum-flux diagnostics; SAM-like circulation indices; jet-location and quadratic-fit diagnostics; file-level ESGF provenance; processing code; reuse examples; and machine-readable quality-control records. All 1,600 source NetCDF subsets were matched against their expected SHA-256 values. The frozen release passed all 447 release-level quality-control checks and all 888 independent numerical reproduction comparisons. Native model grids and distinct HadGEM geopotential-height grid cohorts are retained explicitly to support transparent reuse. The dataset is licensed under Creative Commons Attribution 4.0 International. Users should cite the permanent AntPAMIP-400 repository record and acknowledge the underlying CMIP6/PAMIP modelling institutions and source datasets.