SPI - Standardized Precipitation Index
CliSAP Product (P2)
Access
RESTRICTED only accessable in CEN/MPI net or via CliSAP login What does that mean?
data access via file system:
/data/icdc/climate_indices/standard_precipitation_index_SPI
Description
The "Standardized Precipitation Index" (SPI) is used to describe extremely dry or wet climate situations. The World Meteorological Organization (WMO) recommends, that all national meteorological and hydrological services should use the SPI for monitoring of dry spells (Press report December 2009, WMO No. 872).
The advantages of SPI usage are:
- Only precipitation data are needed for the calculation of the index.
- The index is a standardized measure for precipitation in different climatic regions and for seasonal differences.
- Calculated for different time scales: meteorological, agricultural-economic and hydrological.
Definition of SPI classes
| SPI Wert | Deutung |
|---|---|
| SPI ≤ -2 | Extremely dry |
| -2 < SPI ≤ -1.5 | Severely dry |
| -1.5 < SPI ≤ -1 | Moderately dry |
| -1 < SPI ≤ 1 | Near normal |
| 1 < SPI ≤ 1.5 | Moderately wet |
| 1.5 < SPI ≤ 2 | Severely wet |
| SPI ≥ 2 | Extremely wet |
Calculation
The SPI, presented here, is different from the original SPI definition of McKee et al. 1993. An enhanced SPI is used, that significantly reduces errors resulting from the determination of the precipitation's distribution (Sienz et al. 2011). MC Kee et al. 1993 shifted the time series of the SPI one time step into the future, but this is not done for the calculation of the SPI presented here.
The SPI was calculated from two precipitation data sets:
- European Climate and Data Assessment (ECA&D), E-OBS gridded dataset Version 4.0
- Climate Research Unit (CRU), Version: CRU TS 2.1
Parameters
| Name | Unit |
|---|---|
| Standardized Precipitation Index | dimension less |
| (Time scales: 1, 3, 6, 9, 12, 24 and 48 months) |
Spatial and temporal resolution
SPI (ECA&D Precipitation), Europe
Time period:
- January 1951 to December 2010, monthly
Geographically:
- Longitude 11W to 60E (Resolution: 0.5 degree)
- Latitude 35N to 72N (Resolution: 0.5 degree)
SPI (CRU Precipitation), Europe and USA
Time period:
- January 1951 to December 2010, monthly
Geographically (Europe):
- Longitude 11W to 60E (Resolution: 0.5 degree)
- Latitude 35N to 72N (Resolution: 0.5 degree)
Geographically (USA):
- Longitude 126W to 60W (Resolution: 0.5 degree)
- Latitude 24N to 50N (Resolution: 0.5 degree)
Data quality
The qualityof the SPIcannotbe better than thequality of theprecipitation data used for its calculation.Inhomogeneitiesin the observedtime series,theinterpolationtothe grid,aswell as theirregular distributionof stationsin space andtimealso affect thedatapresented here.On the quality ofECA &Ddata, seeHaylocketal.(2008) andvan denBesselaaretal.(2011) andforCRUdata see Mitchelland Jones(2005).
Contact
Name: Frank Sienz
Institute: MPI
Email: frank.sienz (at) mpimet.mpg.de
at ICDC:
Name: Annika Jahnke-Bornemann
Institute: ICDC, CEN
References
Literature:
- McKee, T.B., Doeskin, N.J. and Kleist, J.: The relationship of drought frequency and duration to timescales, in 8th Conf. on applied climatology, pp. 179-184, American Meteorological Society, Anaheim, Canada, 1993.
- Sienz, F., Bothe, O. and Fraedrich K.: Monitoring and quantifying future climate projections of dryness and wetness extremes: SPI bias. In preparation.
Data ECA&D:
- European Climate and Data Assessment (ECA&D)
- Haylock, M.R., Hofstra, N., Klein Tank, A.M.G., Klok, E.J., Jones, P.D., New, M.: A European daily high-resolution gridded dataset of surface temperature and precipitation. J. Geophys. Res (Atmospheres), 113, D20119, 2008.
- van den Besselaar, E.J.M., Haylock M.R., van der Schrier, G. and Klein Tank, A.M.G.: A European daily high-resolution observational gridded data set of sea level pressure. J. Geophys. Res., 116, D11110, 2011.
Data CRU:
