Abstract. An analysis was made of the Precipitation Concentration Index using the new MOPREDAS database of monthly precipitation in Spain (Monthly Precipitation Data base of Spain). The database was compiled after exhaustive quality control of the complete digitalized Spanish Meterological Agency (AEMet) archives and contains a total set of 2670 complete and homogeneous monthly precipitation series from 1946 to 2005. Thus, MOPREDAS currently holds the densest information available for the 1946-2005 period for Spain and ensures a high resolution of results. The Precipitation Concentration Index (PCI) is a powerful indicator of the temporal distribution of precipitation, traditionally applied at annual scales; as the value increases, the more concentrated the precipitation. Furthermore PCI is a part of the well-known Fournier index, with a long tradition on natural system analyses, as for example soil erosion. In this paper, the mean values of annual, seasonal and wet and dry periods of PCI in the conterminous Spain and for two normal periods (1946-1975 and 1976-2005) were studied.Precipitation in Spain follows a general NW-SE spatial pattern during the wet (months) period due to the Atlantic storm track, while during the dry (months) period, it follows a predominantly N-S spatial pattern. As a result, the annual values of PCI combine the two patterns and show a SW-NE PCI gradient.The analyses of the two sub-periods show significant changes in the precipitation occurred in conterminous Spain from 1946 to 2005, and precipitation concentration increased across most of the IP. At an annual scale, PCI increases mostly due to an increase in precipitation concentration during the wet season. At a seasonal scale significant changes were detected between 1945 -1975 and 1976, while changes in Correspondence to: J. C. González-Hidalgo (jcgh@posta.unizar.es) winter, spring and summer were mostly localized and not generalized (both increase and decrease). Changes in PCI seem to be complex and appear to be related to global atmospheric features and synoptic and local factors affecting precipitation trends. We discuss the possible explanation linked to the atmospheric pattern and monthly trends and their implications.

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Abstract.A high-resolution daily gridded precipitation dataset was built from raw data of 12 858 observatories covering a period from 1950 to 2012 in peninsular Spain and 1971 to 2012 in Balearic and Canary islands. The original data were quality-controlled and gaps were filled on each day and location independently. Using the serially complete dataset, a grid with a 5 × 5 km spatial resolution was constructed by estimating daily precipitation amounts and their corresponding uncertainty at each grid node. Daily precipitation estimations were compared to original observations to assess the quality of the gridded dataset. Four daily precipitation indices were computed to characterise the spatial distribution of daily precipitation and nine extreme precipitation indices were used to describe the frequency and intensity of extreme precipitation events. The Mediterranean coast and the Central Range showed the highest frequency and intensity of extreme events, while the number of wet days and dry and wet spells followed a north-west to south-east gradient in peninsular Spain, from high to low values in the number of wet days and wet spells and reverse in dry spells. The use of the total available data in Spain, the independent estimation of precipitation for each day and the high spatial resolution of the grid allowed for a precise spatial and temporal assessment of daily precipitation that is difficult to achieve when using other methods, pre-selected long-term stations or global gridded datasets. SPREAD dataset is publicly available at https://doi.org/10.20350/digitalCSIC/7393.

This is a study of the changes in annual and seasonal precipitation amounts and variability, during the period 1951-2000, using MOPREDA MES . This dataset includes 1113 complete and homogeneous monthly precipitation time series from the Mediterranean Iberian Peninsula (IP), and corresponds to the five official Spanish hydrological divisions which drain into the Mediterranean Sea. The time series of annual and seasonal precipitation were used to test for trends. The absolute value of the anomaly time series was also tested for trends to identify changes in interannual variability of precipitation. The significance of these changes was assessed using the non-parametric Spearman rank test. The intensities of observed changes, both on mean values and variability, were estimated by using linear regression techniques. Finally, we analysed the area affected by different trends by using raster maps and spatial statistics, in addition to calculating the global balances for the five hydrological divisions. We detected high variability in precipitation regimes and conditions in the study area; nevertheless, a decrease in seasonal and annual precipitation has predominated in the east of the IP during the second half of the 20th century. On an annual scale, precipitation has diminished over 90.1% of the study area. Additionally, a high percentage of the territory was affected by diminishing precipitation at a seasonal level: 85% (of territory) in summer, 82% in spring, 64% during winter and 61% in autumn. Taking the study area as a whole, seasonal precipitation decreases are ranked as follows: summer (−22.5%), spring (−19.3%), winter (−7.3%), and autumn (−5.2%), with a decrease in the value of the global mean annual precipitation −12.4%. We also detected an increase of precipitation variability in winter (+23.5%) and summer (+11.4%), and a decrease in autumn and spring (−14.9 and −16.8%, respectively) with a global mean value of +7.8%.

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An analysis of the spatial and temporal variability of daily precipitation concentration (CI) in Spain was made based on a high‐resolution (5 × 5 km) daily gridded precipitation data set for the 1950–2012 period. For each grid point in the Iberian Peninsula (IP) and Balearic and Canary Islands, the average annual CI was computed, as well as its coefficient of variation and the 5th and 95th percentiles. Annual values were also computed, and the time series of the index were used to assess temporal trends over the whole period. The spatial distribution of the CI showed a strong relationship with the orographic barriers near the coastlines. The Canary Islands showed the highest values of CI, along with the eastern Mediterranean facade of the IP. The highest inter‐annual variations of the CI occurred in the southern IP and in the southern Canary Islands. The trends of CI were, overall, positive and significant, which indicates an increase of daily precipitation concentration over the study period and an increasing environmental risks scenario where erosivity, torrentiality, and floods may become more frequent.

The risk of erosion and desertification is one of the main environmental concerns in the Mediterranean Iberian Peninsula. Changes in precipitation are expected in Mediterranean areas because of climate change, but predictions are not certain. For this reason, dense precipitation databases are required to explore observed changes in the amount, concentration and variability of precipitation, to gain a clearer understanding of the dynamics involved in the main climatological agent of erosion. For this study, we took the recently developed MOPREDA MES dataset, which includes 1113 complete and homogeneous monthly rainfall series from the Mediterranean fringe of the Iberian Peninsula (IP) covering the period 1951-2000. These were used to calculate and analyse trends in Total Annual Precipitation (P t ), the Precipitation Concentration Index (PCI) and Modified Fourier Index (MFI). Our results show that, although there were decreases in annual rainfall, increases in the concentration of precipitation also predominated in the Mediterranean Iberian Peninsula during the period 1951-2000. However, spatial variability of these trends is high, and changes in rainfall erosivity exhibit a complex spatial pattern. Thus, decreases in rainfall erosivity are detected under semiarid conditions (Central Ebro basin and South East IP), while increases mainly occur in dry and subhumid areas. We present a detailed spatial description of the results and discuss their implication for the risk of erosion and desertification in different regions of the study area.

The growth of past, present, and future forests was, is and will be affected by climate variability. This multifaceted relationship has been assessed in several regional studies, but spatially resolved, large-scale analyses are largely missing so far. Here we estimate recent changes in growth of 5800 beech trees (Fagus sylvatica L.) from 324 sites, representing the full geographic and climatic range of species. Future growth trends were predicted considering state-of-the-art climate scenarios. The validated models indicate growth declines across large region of the distribution in recent decades, and project severe future growth declines ranging from −20% to more than −50% by 2090, depending on the region and climate change scenario (i.e. CMIP6 SSP1-2.6 and SSP5-8.5). Forecasted forest productivity losses are most striking towards the southern distribution limit of Fagus sylvatica, in regions where persisting atmospheric high-pressure systems are expected to increase drought severity. The projected 21st century growth changes across Europe indicate serious ecological and economic consequences that require immediate forest adaptation.