Description
The 9-month Standardized Precipitation Index (SPI-9) is a meteorological drought indicator to monitor precipitation anomalies over 9-month accumulation periods and is a proxy indicator for medium-term impacts, for example reduced stream flow and reservoir storage. 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.
Contact
Contributors
-
- European and Global Drought Observatories, EDO
How to cite
European Commission, Joint Research Centre (JRC) (2024): GDO Standardized Precipitation Index ERA5, 9-month accumulation period (SPI-9) (version 2.0.0). European Commission, Joint Research Centre (JRC) [Dataset] PID: http://data.europa.eu/89h/3e0368e9-e55a-4d6e-bcbf-296de8e43578
Keywords
Copernicus Drought ECMWF ERA5 European Drought Observatory (EDO) Global Drought Observatory (GDO) Precipitation Precipitation Anomaly SPI CEMS
Data access
Factsheet
Publications
Geographic areas
Spatial coverage
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---|---|
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WKT | POLYGON ((-180 90, 180 90, 180 -90, -180 -90, -180 90)) |
Temporal coverage
From date | To date |
---|---|
1982-01-01 | N/A |
Additional information
- Published by
- European Commission, Joint Research Centre
- Created date
- 2024-03-25
- Modified date
- 2024-07-12
- Issued date
- 2024-03-25
- Landing page
- https://drought.emergency.copernicus.eu/
- Language(s)
- English
- Data theme(s)
- Environment
- Update frequency
- monthly
- Identifier
- http://data.europa.eu/89h/3e0368e9-e55a-4d6e-bcbf-296de8e43578
- Popularity
- 30 Nov 2024: 1 visits