A Multiscalar Drought Index Sensitive to Global Warming: The Standardized Precipitation Evapotranspiration Index

The authors propose a new climatic drought index: the standardized precipitation evapotranspiration index (SPEI). The SPEI is based on precipitation and temperature data, and it has the advantage of combining multiscalar character with the capacity to include the effects of temperature variability o...

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Bibliographic Details
Published in:	Journal of climate 2010-04, Vol.23 (7), p.1696-1718
Main Authors:	VICENTE-SERRANO, Sergio M, BEGUERIA, Santiago, LOPEZ-MORENO, Juan I
Format:	Article
Language:	eng
Subjects:	Climate change Climatic indexes Climatology. Bioclimatology. Climate change Drought Drought analysis Drought index Earth, ocean, space Evapotranspiration Evapotranspiration-precipitation relationships Exact sciences and technology External geophysics General circulation models Global warming Groundwater Hydrology Meteorology Monitoring systems Observatories Periodical indexing Precipitation Probability distribution Probability theory Rain Standardized precipitation index Temperature Temperature data Temperature effects Temperature variability Variables Water balance Water demand Water in the atmosphere (humidity, clouds, evaporation, precipitation) Water shortages Water temperature
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Summary:	The authors propose a new climatic drought index: the standardized precipitation evapotranspiration index (SPEI). The SPEI is based on precipitation and temperature data, and it has the advantage of combining multiscalar character with the capacity to include the effects of temperature variability on drought assessment. The procedure to calculate the index is detailed and involves a climatic water balance, the accumulation of deficit/surplus at different time scales, and adjustment to a log-logistic probability distribution. Mathematically, the SPEI is similar to the standardized precipitation index (SPI), but it includes the role of temperature. Because the SPEI is based on a water balance, it can be compared to the self-calibrated Palmer drought severity index (sc-PDSI). Time series of the three indices were compared for a set of observatories with different climate characteristics, located in different parts of the world. Under global warming conditions, only the sc-PDSI and SPEI identified an increase in drought severity associated with higher water demand as a result of evapotranspiration. Relative to the sc-PDSI, the SPEI has the advantage of being multiscalar, which is crucial for drought analysis and monitoring.
ISSN:	0894-8755 1520-0442