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

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This dataset provides Standardised Precipitation Index (SPI) time series for the United Kingdom's Integrated Hydrological Units Hydrometric Areas, covering 1961 to 2012. SPI is a drought index derived from the probability of precipitation over a given accumulation period, following McKee et al. (1993), and is calculated for 1, 3, 6, 12, 18 and 24-month accumulation periods, each computed for every calendar month. The gamma distribution used for the index was fitted to the standard reference period 1961-2010. Monthly and longer-period series may show autocorrelation. It is published by the Environmental Information Data Centre, building on the Integrated Hydrological Units delineation by Kral, Fry and Dixon (2015).Standardised Precipitation Index (SPI) data for Integrated Hydrological Units (IHU) Hydrometric Areas (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: Hydrometric Areas without Coastline. NERC-Environmental Information Data Centre doi:10.5285/3a4e94fc-4c68-47eb-a217-adee2a6b02b3 [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/10.5285/5e1792a0-ae95-4e77-bccd-2fb456112cc1.