HR: 10:50h
AN: H32B-03    [Abstracts]
TI: Statistic versus stochastic characterization of persistent droughts
AU: * Gonzalez-Perez, J
EM: javier.gonzalez@uclm.es
AF: University of Castilla La Mancha, Dept. of Civil Engineering, Avda Camilo Cela s/n, Ciudad Real, 13071 Spain
AU: Valdes, J B
EM: jvaldes@u.arizona.edu
AF: The University of Arizona, Dept. of Civil Engineering and Eng Mechanics, Tucson, AZ 85721 United States
AB: Droughts are one of more devastating natural disasters. A drought event is always related with deficiency in precipitation over a time period. As longer are the drought periods, larger are the damages associated with, following a potential relationship. Additionally, the extension covered by an event also increases its impact, because it makes difficult to compensate the deficit from neighbourhood water resources. Therefore, the characterization of a drought by its persistent deficit, and the area over which it extends are main points to be carried on. The Standardized Precipitation Index (SPI) provides a statistical characterization of the deficits. Its computation, for different aggregation time scales, allows a persistence evaluation. Another more recent statistic that may be applied in drought characterization is the extreme persistent probability function (e.p.f.), which characterizes the persistence of extreme realizations in a random sequence. This work presents an analysis of the differences in performance of the SPI and the e.p.f. in the statistical characterization of a drought event. The inclusion of the persistency directly in the statistic gives to the e.p.f. an advantage over the SPI. Furthermore, the relationship between the e.p.f. and its mean frequency of recurrence is known. Thus, the e.p.f. may be applied to provide either statistic or stochastic characterization of a drought event. Both criteria were compared, showing that the stochastic characterization produces a better drought indicator. The stochastic characterization using the e.p.f. as a criterion yields the new Drought Frequency Index (DFI). The index is applicable to any random water related variable to identify drought events. Its main advantages over the SPI are the direct inclusion of persistence, and its larger robustness to the time scale. To incorporate the spatial extension in the characterization of a drought event, the new DFI may also be evaluated to characterize the drought spatial-temporal development using DFI-maps. Case studies in Spain and the USA support the advantages of the e.p.f.
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1812 Drought
DE: 1817 Extreme events
DE: 1833 Hydroclimatology
DE: 1869 Stochastic hydrology
SC: Hydrology [H]
MN: Fall Meeting 2005