dataset · Global

Monthly drought indices from 1940 to present derived from ERA5 reanalysis

ERA5–Drought is a global reconstruction of drought indices from 1940 to present. The dataset comprises two standardised drought indices: - the Standardised Precipitation Index (SPI) - the Standardised Precipitation-Evapotranspiration Index (SPEI). The SPI measures the precipitation deficit that accumulated over the preceding months and evaluates the deficit with respect to a reference period. The SPEI is an extension of the SPI and incorporates potential evapotranspiration to capture the impact

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Source details

Licence: CC-BY-4.0

Evidence quality: 53.9

Listed in cds public catalogue API on 2026-10-16; relevance/value screened (haiku).

Metadata checked: 2026-10-14T13:20:00.000Z

What's in it

Data offered docs-verified: Standardised Precipitation Index (SPI) · Standardised Precipitation-Evapotranspiration Index (SPEI) · SPI probability of zero precipitation (P0) · SPEI and SPI normality test (alpha 0.05)
Coverage docs-verified: Global (90N-90S, 180W-180E) · January 1940 to near real time
Resolution llm-inferred: 0.25° x 0.25° regular latitude-longitude grid; monthly temporal resolution
Update frequency docs-verified: Monthly. Intermediate dataset is updated in near real time; consolidated dataset has a 2-3 month delay.
Formats docs-verified: NetCDF
Access llm-inferred: Open CC-BY-4.0 licence (per ENTRY). Download is via the Copernicus Climate Data Store, whose page shows Login / Register; ENTRY lists no API key (auth null).

Useful for

Use cases llm-inferred: Long-term drought severity context (SPI/SPEI at 1-48 month windows) for UK-wide water resource or abstraction licence reviews · Antecedent dry-period screening alongside flood risk or drainage studies, using monthly SPI/SPEI as an input · Climate-driven drought baseline for ecological or habitat condition assessments, with a clear caveat that 0.25° is coarse · Comparing ERA5 single-realisation and ensemble SPI/SPEI to show drought uncertainty in planning reports
Audience llm-inferred: hydrologists · water resources engineers · flood risk consultants · drainage engineers · ecologists · climate risk analysts · GIS analysts

Limitations

Constraints llm-inferred: Global 0.25° grid (roughly 25 km cells) is too coarse for site-scale or small-catchment work · Derived from ERA5 reanalysis, not gauge observations, so it inherits reanalysis biases · Consolidated data lags real time by 2-3 months, so the most recent months are provisional · Reference period 1991-2020 is fixed; a change to it would be a major version revision · No UK-specific calibration or validation is described in the docs · Not a UK catchment-scale tool; needs further processing (e.g. area-in-drought calculations) using the guidelines

Evidence

Check upstream coverage, uncertainty and licence before use. Station observations are not forecasts or design levels.