Spatial analysis of rainfall trends in the region of Valencia (East Spain)

This paper examines the spatial and temporal rainfall characteristics of th e region of Valencia, Western Mediterranean Basin least Spain), during the World Meteorological Organization (WMO) normal period 1961-1990. The study used a dense and homogeneous daily precipitation database comprising 97 rai n-gauge stations. Total and monthly rainfall concentrations have been studi ed in the context of their mean values, interannual variability and spatial diversification. Trends have been analysed using both parametric and non-p arametric tests. In order to establish the spatial distribution of rainfall patterns and to detect homogeneous areas with similar rainfall evolution, a statistic based on the Cramer-von Mises test is proposed. The kriging int erpolation methods for characterizing the magnitude of observed changes is used. Areas with contrasting rainfall evolution are identified. In more humid are as, a significant decrease in annual rainfall associated with significant i ncreases in interannual rainfall variability is observed. In inland zones, decreases in total annual rainfall and increases in interannual variability are less clear, but there are indications of an increase in monthly rainfa ll concentration. In these inland zones, where more forest and woodland are as are located and forest fires are frequent, the observed trends could gre atly affect desertification through changes in the disturbance regime. In m ore arid areas, local variability in rainfall evolution is higher and no si gnificant changes can be defined. Copyright (C) 2000 Royal Meteorological S ociety.