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GDO Standardized Precipitation Index ERA5, 12-month accumulation period (SPI-12) (version 2.0.0)

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The 12-month Standardized Precipitation Index (SPI-12) is a meteorological drought indicator to monitor precipitation anomalies over 12-month accumulation periods and is a proxy indicator for medium-term impacts, for example reduced stream flow and reservoir storage, and for long-term impacts, for example reduced reservoir and groundwater recharge. This indicator is derived from the fifth generation ECMWF reanalysis for the global climate and weather ERA5 (https://confluence.ecmwf.int/display/CKB/The+family+of+ERA5+datasets) hourly precipitation data; using a reference period between the year 1991 and 2020. The SPI represents precipitation anomalies at a given location and time, as the deviation from the long-term mean in a standard-normal distribution, with more negative values representing a more severe drought. SPI is calculated by comparing the observed total precipitation amounts for an accumulation period of a number of months, indicated by a number following SPI-, with the long-term “climatological” rainfall distribution for that same period of the year, derived from historical rainfall records in a specific reference period. A given accumulation period corresponds to different potential impacts of a drought, with shorter accumulation periods generally representing fast-changing aspects of the water system such as surface soil moisture and flow in small rivers, and longer accumulation periods representing slower changing aspects of the water system such as groundwater and baseflow in larger rivers. However, the exact relationship between accumulation period and impacts depends on the natural environment (e.g. geology, soils) and human interference (e.g. irrigation). Details on the calculation of the SPI are given in the indicator factsheet.

Contributors

EDO European and Global Drought Observatories

How to cite

European Commission, Joint Research Centre (2026): GDO Standardized Precipitation Index ERA5, 12-month accumulation period (SPI-12) (version 2.0.0). [Dataset] doi: 10.2905/JRC.0FGQTQ8 PID: http://data.europa.eu/89h/d8010f97-4ca9-4a5d-883d-455f85d03408

Keywords

CEMSCopernicusDroughtECMWFERA5European Drought Observatory (EDO)Global Drought Observatory (GDO)PrecipitationPrecipitation AnomalySPI

Data access

Data Download Service (NetCDF)
NetCDF

NetCDF is a set of software libraries and self-describing, machine-independent data formats that support the creation, access and sharing of array-oriented scientific data.
Downloadable file

A downloadable file for the dataset.

Use conditions
Creative Commons Attribution 4.0 International

CC BY 4.0 lets others distribute, remix, tweak, and build upon the author’s work, even commercially, as long as they credit the author for the original creation. This is the most accommodating of licences offered. Recommended for maximum dissemination and use of licenced materials.

Access conditions
No limitations

Anybody can directly and anonymously access the data, without being required to register or authenticate.

Data Download Service (GeoTIFF)
TIFF

TIFF – Tagged Image File Format – is a computer file format for storing raster graphics images, popular among graphic artists, the publishing industry and photographers. TIFF is widely supported by scanning, faxing, word processing, optical character recognition, image manipulation, desktop publishing and page-layout applications. The format was created by Aldus Corporation for use in desktop publishing.
Downloadable file

A downloadable file for the dataset.

Use conditions
Creative Commons Attribution 4.0 International

CC BY 4.0 lets others distribute, remix, tweak, and build upon the author’s work, even commercially, as long as they credit the author for the original creation. This is the most accommodating of licences offered. Recommended for maximum dissemination and use of licenced materials.

Access conditions
No limitations

Anybody can directly and anonymously access the data, without being required to register or authenticate.

Data Download Service URL
NetCDF

NetCDF is a set of software libraries and self-describing, machine-independent data formats that support the creation, access and sharing of array-oriented scientific data.
Downloadable file

A downloadable file for the dataset.

Use conditions
European Commission reuse notice

According to the European Commission reuse notice, reuse is authorised, provided the source is acknowledged. The reuse policy of the European Commission is implemented by the Decision of 12 December 2011. The general principle of reuse can be subject to conditions which may be specified in individual copyright notices. Therefore users are advised to refer to the copyright notices of the individual websites maintained under Europa and of the individual documents. Reuse is not applicable to documents subject to intellectual property rights of third parties.

Access conditions
No limitations

Anybody can directly and anonymously access the data, without being required to register or authenticate.

Other resources

Standardized Precipitation Index (SPI) Factsheet
PDF

PDF – Portable Document Format – is a file format developed to present documents, including text formatting and images, in a manner independent of application software, hardware and operating systems. Based on the PostScript language, each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, vector graphics, raster images and other information needed to display it. PDF was standardized as an open format and does not require any royalties for its implementation.

Use conditions
European Commission reuse notice

According to the European Commission reuse notice, reuse is authorised, provided the source is acknowledged. The reuse policy of the European Commission is implemented by the Decision of 12 December 2011. The general principle of reuse can be subject to conditions which may be specified in individual copyright notices. Therefore users are advised to refer to the copyright notices of the individual websites maintained under Europa and of the individual documents. Reuse is not applicable to documents subject to intellectual property rights of third parties.

Access conditions
No limitations

Anybody can directly and anonymously access the data, without being required to register or authenticate.

  • Factsheet

Publications

Publication
The relationship of drought frequency and duration to time scale.
McKee, T.B., N.J. Doesken and J. Kleist. 1993. The relationship of drought frequency and duration to time scale. In: Proceedingsof the Eighth Conference on Applied Climatology, Anaheim, California, 17–22 January 1993. Boston, American Meteorological Society, 179–184

Spatial coverage

Temporal coverage

From date To date
1982-01-01 N/A

Additional information

Published by
European Commission, Joint Research Centre
Contact email
JRC-EMS-DROUGHT (at) ec.europa.eu
Update frequency
monthly

The event occurs once a month.

Language(s)
English

English is a member of the West Germanic group of the Germanic languages. It is an official language of almost 60 sovereign states and is now a global lingua franca.It is the third-most-common native language in the world and it is widely learned as a second language.

Data theme(s)
Environment

dataset theme covering the domain of environment, defined as the interaction of all living species, climate, weather, and natural resources that impact human survival and economic activity

Geographical name(s)
World
Issued date
2024-03-25
Created date
25 Mar 2024 18:16
Modified date
21 Mar 2025 14:48
Landing page
https://drought.emergency.copernicus.eu/ 
Dataset identifier
http://data.europa.eu/89h/d8010f97-4ca9-4a5d-883d-455f85d03408
Other identifiers
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