title: Testing universality in critical exponents: The case of rainfall.
abstract: One of the key clues to consider rainfall as a self-organized critical phenomenon is the existence of power-law distributions for rain-event sizes. We have studied the problem of universality in the exponents of these distributions by means of a suitable statistic whose distribution is inferred by several variations of a permutational test. In contrast to more common approaches, our procedure does not suffer from the difficulties of multiple testing and does not require the precise knowledge of the uncertainties associated to the power-law exponents. When applied to seven sites monitored by the Atmospheric Radiation Measurement Program the tests lead to the rejection of the universality hypothesis, despite the fact that the exponents are rather close to each other. We discuss the reasons of the rejection.
authors.affiliation: Max Planck Institute for the Physics of Complex Systems, Noethnitzer Str. 38, D-01187 Dresden, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Deluca
authors.affiliation: Departament de Matemàtiques, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallés, Spain.
authors.forename: Pedro
authors.initials: P
authors.lastname: Puig
authors.affiliation: Departament de Matemàtiques, Universitat Autònoma de Barcelona, E-08193 Cerdanyola del Vallés, Spain.|Centre de Recerca Matemàtica, Campus de Bellaterra, Edifici C, E-08193 Barcelona, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Corral