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Standardised Precipitation Index (SPI) data for different levels of Integrated Hydrological Units (IHU). SPI is a drought index based on the probability of precipitation for a given accumulation period as defined by McKee et al . SPI is calculated for different accumulation periods: 1, 3, 6, 12, 18, 24 months. Each of these is in turn calculated for each of the twelve calendar months. Note that values in monthly (and for longer accumulation periods also annual) time series of the data therefore are likely to be autocorrelated. The standard period which was used to fit the gamma distribution is 1961-2010. The datasets cover the period from 1961 to 2012.  McKee, T. B., Doesken, N. J., Kleist, J. (1993). The Relationship of Drought Frequency and Duration to Time Scales. Eighth Conference on Applied Climatology, 17-22 January 1993, Anaheim, California.
Publication date: 2015-05-22 ( created 2015-05-14 )
Supporting information available to assist in re-use of this dataset.
IHU Hydrometric Areas
Link to the Integrated Hydrological Units dataset which was used to produce the SPI time series for IHU Hydrometric Areas.
CEH droughts portal
Link to the CEH droughts portal where SPI time series can be visualised and downloaded
Lineage of children datasets explained in their metadata records