In the last half of the twentieth century, the precipitation regime on the Spanish east coast showed an overall pattern of reduction in precipitation totals. This work presents the results from a novel procedure to disaggregate the precipitation series in the Valencia region on the basis of their meteorological origin. Important differences are found between specific trends and changes in the contributions from 1) Atlantic frontal systems, 2) convective–orographic storms, and 3) easterly advections over the Mediterranean Sea (backdoor cold fronts). The series for the three components are then used to analyze the evolution, variability, and spatial distribution of the region’s rainfall and to determine the correlations with the North Atlantic Oscillation (NAO) index. The results establish significant differences between inland areas, with a trend toward decreasing precipitation and thus increasing aridity, and coastal areas, with increasing precipitation that tends to be progressively more torrential in nature. Likewise, the correlations with the NAO index also change and show opposite signs for the different components.

A daily rainfall database covering the Júcar and Segura river basin authorities (east Iberian Peninsula, Spain) with high spatial density without gaps (890 series) has been created for the complete period 1955–2016. This has allowed a trend analysis of precipitation and dry/wet spells with a better spatial detail and coverage of key headwaters sectors than previous studies in this area. Results show significant negative trends for precipitation prevailing in Júcar area (an annual average loss of 51 mm), especially towards its north interior headwaters. For this last one the annual loss exceeds 200 mm (20% of precipitation). By contrast, certain pre‐littoral sectors and most of the Segura area are remaining out of these negative trends (some local positive trends). However, the dry spells length and the number of dry days have increased in a generalized way (Júcar and Segura basins) with rainfall concentration in time and space. The decrease of moderate rainfall with greater precipitation effectiveness and weight in the key interior headwaters is the most significant. On the contrary, there has been an increase in extreme torrential rainfall (with poor effectiveness and high risk) at points on the coast and pre‐littoral towards south of the region. These results are linked to a change in the frequency of three basic synoptic types identified in the region as rainfall origin.

The basins of the Júcar and Segura rivers, on the Mediterranean coast of the Iberian Peninsula, present a special water problem and are of particular interest regarding climate change. These basins are very vulnerable to a possible scenario of decreasing water resources. Recent studies on historic rainfall since 1955 have indicated an ongoing loss of precipitation in their headwaters, especially in the case of the Júcar river. The aim of the present study is to perform climate projections for the precipitation variable for several future periods (2021–2040, 2051–2070, 2081–2100) and emission scenarios (RCPs 4.5, 8.5) within the Júcar and Segura River Basin authorities. For this purpose, a set of CMIP5 global models have been used, as well as the CDRD-HR-EIP-1955-2016 database, as a source of local observed information. This database comprises nearly 900 precipitation series in both basins and has been used in recent studies to determine historic trends of change in these basins. A statistical downscaling of the global models for all available observed series has been applied using the LARS-WG method. The results, although variable according to the CMIP5 model used, show the continuation of the patterns of precipitation change in the future, as already observed in the historical series. The results also predict a clear reduction in precipitation in the long term. However, torrential rainfall tends to increase in the coastal areas in relation to that observed in the short-term predictions. These results, due to their high spatial resolution, are of great interest for their use in small-scale hydrological and spatial planning (regional and local), which is one of the current challenges of climate modeling.

Within the area of climate change, summer temperatures are of special interest because of the economic, social and environmental consequences that can derive from their hypothetical increase. A number of recent studies have shown a worldwide trend towards increasing summer temperatures. In this work, we analyse summer temperatures (July and August) in the Valencia region of Spain from 1958 to the present, with the aim of characterising their evolution and detecting any trend towards a higher frequency of warmer days. First results indicate that in our study area there is indeed a higher frequency of days with tropical characteristics and persistent heat; in contrast, we found no tendency to exceed the records of absolute maximum temperatures. Copyright © 2006 Royal Meteorological Society.