Gridded SPEI for Australia 1980-2024 at 0.01-degree resolution derived from ANUClimate v2.0

Standardised Precipitation Evapotranspiration Index (SPEI) at 3, 6, 12, and 24-month timescales for the Australian continent at 0.01-degree (~1 km) resolution, computed for the period January 1980 to December 2024. Derived from ANUClimate v2.0 monthly rainfall, maximum temperature, minimum temperature, and solar radiation using the Hargreaves potential evapotranspiration method and log-logistic distribution fitting. Reference period: January 1980 to December 2009 (30 years). Output period for monthly GeoTIFFs: January 2010 to December 2024. Full-timeseries NetCDF files (540 months, 1980-2024) provided for all four timescales. CRS: GDA94 (EPSG:4283). Missing value (NetCDF): -9999. Source data: ANUClimate v2.0 (Hutchinson et al. 2021, doi:10.25914/60a10acd183a2).

This is the highest resolution (~1 km, 0.01°) continental SPEI dataset available for Australia and the only one derived from ANUClimate v2.0. The closest existing global product is at 5 km resolution (Gebrechorkos et al. 2023, Earth System Science Data).

This work was supported by Western Sydney University and with funding from the Australian Government under the National Environmental Science Program's Resilient Landscapes Hub.

Known limitations:
- SPEI values of -Inf occur in hyper-arid regions and during extreme drought periods where log-logistic distribution fitting fails. These are retained as -Inf in GeoTIFF outputs and stored as missing value (-9999) in NetCDF outputs. See README.md for full details.
- SPEI values within the reference period (January 1980 – December 2009) are self-referential and should be interpreted with caution. The 2010–2024 monthly GeoTIFF outputs are the primary scientific deliverable.

Code developed with AI assistance from Claude (Anthropic). https://claude.ai
See README.md for full methods, known limitations, and reproduction instructions.