Universality in the precipitation and river runoff

For characterizing the inherent dynamical structure of precipitation and river runoffs, we study in representative seasonally detrended records the durations tau where the record is below a given threshold Q. When keeping the return period R-Q of the threshold fixed, we find that the probability density function (PDF) of these durations shows universal features when scaled with the average duration <tau >. For both types of data the scaling function can be approximated by a Gamma-distribution, but also a description by the corresponding PDF of long-term correlated records is possible. The parameters of the PDF depend on the kind of data (precipitation or river runoff) and on R-Q but neither on the climate nor on the hydrological details of the location of the record. Copyright (C) EPLA, 2012