Analysis and objective mapping of extreme daily rainfall in Catalonia

The main objective of this study is to determine the maximum daily precipitation in Catalonia for several established return periods with a high spatial resolution. For this purpose, the maximum daily rainfall annual series from 145 pluviometric stations of the Instituto Nacional de Meteorología (INM) (Spanish Weather Service) in Catalonia have been analyzed. Using the L-moments method of Hosking, every series has been fitted by the extreme value distribution function of Gumbel. From this fitting, the maximum daily precipitation for each of the pluviometric stations corresponding to return periods between 2 and 500 years, have been determined. Applying the Cressman method, the spatial analysis of these values has been achieved. Monthly precipitation climatological data, obtained from the application of Geographic Information Systems (GIS) techniques, have been used as the initial field for the analysis. The maximum daily precipitation at 1 km2 spatial resolution on Catalonia has been objectively determined by the method employed, and structures with wavelength longer than approximately 35 km can be identified. The results show that places where the maximum daily precipitation values are expected are the zone of Guilleries in the Transversal Range, in the highest zones of the Catalan Pyrenees and Cape Creus zone at the northeastern end of Catalonia and in the south, around the Prelittoral Mountain Range between the Mountains of Prades and Montsià. A good fit between the distribution of minimum values and the driest Catalan areas has been found, the lowest values being on the western end of the Central Basin. Copyright © 2006 Royal Meteorological Society.