SPEI web logoSPEI Global Drought Monitor

<-2.33 -1.65 -1.28 -0.84 0 0.84 1.28 1.65 >2.33

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The SPEI Global Drought Monitor offers near real-time information about drought conditions at the global scale, with a 1 degree spatial resolution and a monthly time resolution. SPEI time-scales between 1 and 48 months are provided. The calibration period for the SPEI is January 1950 to December 2010. The starting date of the dataset is 1955 in order to provide common information across the different SPEI time-scales.

The dataset is updated during the first days of the following month based on the most reliable and updated sources of climatic data. Mean temperature data are obtained from the NOAA NCEP CPC GHCN_CAMS gridded dataset. Monthly precipitation sums data are obtained from the 'first guess' Global Precipitation Climatology Centre (GPCC). The CPC data with an original resolution of 0.5º, is interpolated to the resolution of 1º.

Currently, the SPEI Global Drought Monitor is based on the Thortnthwaite equation for estimating potential evapotranspiration, PET. This is due to the lack of real-time data sources for computing more robust PET estimations which have larger data requirements. The main advantage of the SPEI Global Drought Monitor is thus its near real-time character, a characteristic best suited for drought monitoring and early warning purposes. For long-term analysis, however, other datasets are to be preferred that rely on more robust methods of PET estimation. Use of the SPEIbase dataset, which is based on the FAO-56 Penman-Monteith model, is thus recommended for climatological studies of drought.


The data from SPEI Global Drought Monitor is made available under the Open Database License. Any rights in individual contents of the database are licensed under the Database Contents License.

What follows is a human-readable summary of the ODbL 1.0 license. Please, read the full ODbL 1.0 license text for the exact terms that apply.

Users of the dataset are free to:
  • Share: copy, distribute and use the database, either commercially or non-commercially.
  • Create: produce derivative works from the database.
  • Adapt: modify, transform and build upon the database.
Under the following conditions:
  • Attribution: You must attribute any public use of the database, or works produced from the database, by citing one or more of the papers referenced in the References section below. For any use or redistribution of the database, or works produced from it, you must make clear to others the license of the original database.
  • Share-Alike: If you publicly use any adapted version of this database, or works produced from an adapted database, you must also offer that adapted database under the ODbL.

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