We have developed a new monthly temperature database for mainland Spain by using the complete holding of maximum and minimum monthly mean values stored at the Spanish National Meteorological Agency (AEMet). After an exhaustive quality control exercise, the data set includes 1358 complete series, and a high-resolution grid (0.1 ∘ × 0.1 ∘ ) was calculated to analyse monthly trends. There has been an uneven increase in the mean values of maximum and minimum temperatures in the Spanish mainland from 1951 to 2010. The maximum monthly mean temperature values have risen mostly in late winter/early spring and the summer, while the minimum monthly mean temperature values have increased in summer, spring and autumn in southern areas. The spatial pattern of the diurnal temperature range shows a clear north-south gradient in summer, with positive trends in the north and negative trends in the south; furthermore, a negative pattern has been detected in the south in spring and autumn. These areas, particularly the Mediterranean coastland, have been subject to dramatic urbanization and land use changes during the past 30 years that may have affected nocturnal temperatures, in particular. Thus, warming processes in the Iberian Peninsula appear to be influenced both by global factors and more local ones, and their effects should be differentiated spatially.

We analysed long-term variability and trends in meteorological droughts across Western Europe using the Standardized Precipitation Index (SPI). Precipitation data from 199 stations spanning the period 1851-2018 were employed, following homogenisation, to derive SPI-3 and SPI-12 series for each station, together with indices on drought duration and severity. Results reveal a general absence of statistically significant long-term trends in the study domain, with the exception of significant trends at some stations, generally covering short periods. The largest decreasing trends in SPI-3 (i.e., increasing drought conditions) were

ABSTRACT:The most recent debate on global warming focuses on the hiatus in global temperature, for which several explanations have been proposed. On the other hand, spatial variability and nonlinearity in temperature evolution has been recognized as a key point in global change analyses.In this study, we analyse the evolution of the warming rate in the Spanish mainland using the MOTEDAS data set for the last 60 years . Our special emphasis is on the last decades to detect and identify a possible hiatus, and to determine the effects of daytime (T max ) and night-time (T min ) records at annual and seasonal scale on the hiatus. Moving windows running trend analyses were applied to calculate temperature trend and significance for any temporal window from the beginning to the end of the series, ranging from 20 years to the whole series length (60 years)The results suggest that the warming rate in the Spanish mainland reached a maximum between 1970 and 1990, followed by a decrease in intensity in both T max and T min until the present. Furthermore, the decrease in the warming rate in T max has been higher than in T min for the last three decades; therefore, recent annual warming rates appears to depend more on T min than on T max . Significant trends disappear from the middle of the 1980s at any temporal window length in both T max and T min at annual and seasonal scales except in spring T min .Some differences among seasons are evident and, during the last few decades, the highest rates of warming are found in spring and summer, with T max and T min behaving in different ways. This study highlights how the warming rate is highly dependent on the length of the period analysed.

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The standardized precipitation evapotranspiration index (SPEI) is one of the well‐established drought metrics worldwide. It is simply computed using precipitation and atmospheric evaporative demand (AED) data. Although AED is considered a key driver of drought variability worldwide, it could have less impact on drought in specific regions and for particular times as a function of the magnitude of precipitation. Specifically, the influence of the AED might overestimate drought severity during both normal and humid periods, resulting in “false alarms” about drought impacts on physical and human environments. Here, we provided a global characterization of the sensitivity of the SPEI to changes of the AED. Results demonstrate that the contribution of AED to drought severity is largely impacted by the spatial and temporal variability of precipitation. Specifically, the impact of AED on drought severity was more pronounced during periods of low precipitation, compared to wet periods. Interestingly, drought severity in humid regions (as revealed by SPEI) also showed low sensitivity to AED under drier conditions. These results highlight the skill of SPEI in identifying the role of AED in drought evolution, especially in arid and semiarid regions whose climate is characterized typically by low precipitation. This advantage was also evident for humid environments, where SPEI did not overestimate drought severity due to the increased AED. These findings highlight the broader applicability of SPEI to accurately characterize drought severity worldwide.

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We present a long-term assessment of precipitation trends in Southwestern Europe (1850–2018) using data from multiple sources, including observations, gridded datasets and global climate model experiments. Contrary to previous investigations based on shorter records, we demonstrate, using new long-term, quality controlled precipitation series, the lack of statistically significant long-term decreasing trends in precipitation for the region. Rather, significant trends were mostly found for shorter periods, highlighting the prevalence of interdecadal and interannual variability at these time-scales. Global climate model outputs from three CMIP experiments are evaluated for periods concurrent with observations. Both the CMIP3 and CMIP5 ensembles show precipitation decline, with only CMIP6 showing agreement with long term trends in observations. However, for both CMIP3 and CMIP5 large interannual and internal variability among ensemble members makes it difficult to identify a trend that is statistically different from observations. Across both observations and models, our results make it difficult to associate any declining trends in precipitation in Southwestern Europe to anthropogenic forcing at this stage.

The purpose of this research was to identify major drought events on the Spanish mainland between 1961 and 2014 by means of two drought indices, and analyze the spatial propagation of drought conditions. The indices applied were the standardized precipitation index (SPI) and the standardized evaporation precipitation index (SPEI). The first was calculated as standardized anomalies of precipitation at various temporal intervals, while the second examined the climatic balance normalized at monthly scale, incorporating the relationship between precipitation and the atmospheric water demand. The daily meteorological data from Spanish Meteorological Archives (AEMet) were used in performing the analyses. Within the framework of the DESEMON project, original data were converted into a high spatial resolution grid (1.1 km 2) following exhaustive quality control. Values of both indices were calculated on a weekly scale and different timescales (12, 24 and 36 months). The results show that during the first half of the study period, the SPI usually returned a higher identification of drought areas, while the reverse was true from the 1990s, suggesting that the effect from atmospheric evaporative demand could have increased. The temporal propagation from 12-to 24-month and 36-month timescales analyzed in the paper seems to be a far from straightforward phenomenon that does not follow a simple rule of time lag, because events at different temporal scales can overlap in time and space. Spatially, the propagation of drought events affecting more than 25% of the total land indicates the existence of various spatial gradients of drought propagation, mostly east-west or west-east, but also north-south have been found. No generalized episodes were found with a radial pattern, i.e., from inland to the coast.