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Standardised Precipitation Index time series for Integrated Hydrological Units Groups (1961-2012)

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This dataset provides Standardised Precipitation Index (SPI) time series for Integrated Hydrological Units (IHU) groups in the United Kingdom, published by the Environmental Information Data Centre. SPI is a drought index based on the probability of precipitation over a given accumulation period, following McKee et al. (1993). Values are calculated for accumulation periods of 1, 3, 6, 12, 18 and 24 months, each computed separately for every calendar month, meaning monthly and longer-period series may be autocorrelated. The gamma distribution used was fitted to the 1961-2010 standard period, and the dataset itself spans 1961 to 2012, supporting hydrological drought analysis across UK catchment groupings.Standardised Precipitation Index (SPI) data for Integrated Hydrological Units (IHU) groups (Kral et al. [1]). SPI is a drought index based on the probability of precipitation for a given accumulation period as defined by McKee et al. [2]. 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 dataset covers the period from 1961 to 2012. [1] Kral, F., Fry, M., Dixon, H. (2015). Integrated Hydrological Units of the United Kingdom: Groups. NERC-Environmental Information Data Centre https://doi.org/10.5285/f1cd5e33-2633-4304-bbc2-b8d34711d902 [2] 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. Full details about this dataset can be found at https://doi.org/10.5285/dfd59438-2170-4472-b810-bab33a83d09f.