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Choice of an improper probability distribution may impart bias to the index values, exaggerating or minimizing drought severity. This study compares a suite of candidate probability distributions for use in<jats:styled-content style=\"fixed-case\">SPI<\/jats:styled-content>and<jats:styled-content style=\"fixed-case\">SPEI<\/jats:styled-content>normalization using the 0.5\u00b0 \u00d7 0.5\u00b0 gridded Watch Forcing Dataset (<jats:styled-content style=\"fixed-case\">WFD<\/jats:styled-content>) at the continental scale, focusing on Europe. Several modifications to the<jats:styled-content style=\"fixed-case\">SPI<\/jats:styled-content>and<jats:styled-content style=\"fixed-case\">SPEI<\/jats:styled-content>methodology are proposed, as well as an updated procedure for evaluating<jats:styled-content style=\"fixed-case\">SPI<\/jats:styled-content>\/<jats:styled-content style=\"fixed-case\">SPEI<\/jats:styled-content>goodness of fit based on the Shapiro\u2013Wilk test. Candidate distributions for<jats:styled-content style=\"fixed-case\">SPI<\/jats:styled-content>organize into two groups based on their ability to model short\u2010term accumulation (1\u20132 months) or long\u2010term accumulation (&gt;3 months). The two\u2010parameter gamma distribution is recommended for general use when calculating<jats:styled-content style=\"fixed-case\">SPI<\/jats:styled-content>across all accumulation periods and regions within Europe, in agreement with previous studies. The generalized extreme value distribution is recommended when computing the<jats:styled-content style=\"fixed-case\">SPEI<\/jats:styled-content>, in disagreement with previous recommendations.<\/jats:p>","DOI":"10.1002\/joc.4267","type":"journal-article","created":{"date-parts":[[2015,2,19]],"date-time":"2015-02-19T16:22:49Z","timestamp":1424362969000},"page":"4027-4040","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":742,"title":["Candidate Distributions for Climatological Drought Indices (<scp>SPI<\/scp>and<scp>SPEI<\/scp>)"],"prefix":"10.1002","volume":"35","author":[{"given":"James H.","family":"Stagge","sequence":"first","affiliation":[{"name":"Department of Geosciences University of Oslo Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lena M.","family":"Tallaksen","sequence":"additional","affiliation":[{"name":"Department of Geosciences University of Oslo Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lukas","family":"Gudmundsson","sequence":"additional","affiliation":[{"name":"Institute for Atmospheric and Climate Science ETH Zurich Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2308-0392","authenticated-orcid":false,"given":"Anne F.","family":"Van Loon","sequence":"additional","affiliation":[{"name":"Hydrology and Quantitative Water Management Group Wageningen University The Netherlands"},{"name":"School of Geography, Earth and Environmental Sciences University of Birmingham UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kerstin","family":"Stahl","sequence":"additional","affiliation":[{"name":"Institute of Hydrology University of Freiburg Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2015,2,19]]},"reference":[{"key":"e_1_2_9_2_1","doi-asserted-by":"publisher","DOI":"10.1109\/TAC.1974.1100705"},{"key":"e_1_2_9_3_1","unstructured":"AllenR PereiraL RaesD SmithM.1998. 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