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Droughts are probably the natural hazard with the highest socioeconomic impact. Simultaneously, they are a very complex phenomenon; they are triggered by a diversity of physical factors and occur at a variety of time scales. Consequently, the instrumental record currently available is too short and the characterization of its multidecadal variability requires the use of natural proxies (tree rings, sedimentary records) or documentary sources. In this paper we analyse three documentary sources with potential to analyse the long-term variability of droughts: chapter acts, logbooks and chronicles. The chapter acts recorded discussions and decisions made during the assemblies of the local authorities and provide continuous and direct evidence on drought impacts. They are especially useful to study droughts between the 15th and the 19th centuries in Europe and the 17th to 18th in the former colonies. Logbooks recorded the meteorological conditions and the incidents occurred during navigation. They provide indirect information through the circulation indices that can be very helpful to understand the mechanisms and teleconnections associated to droughts. Finally, the chronicles are historiographical documents describing political and social events. They are secondary sources and the references to climatic events are discontinuous, thus their analysis must be extremely careful, but they are especially useful to study specific drought events especially prior to 15th century when no other sources are available.

Droughts are probably the natural hazard with the highest socioeconomic impact. Simultaneously, they are a very complex phenomenon; they are triggered by a diversity of physical factors and occur at a variety of time scales. Consequently, the instrumental record currently available is too short and the characterization of its multidecadal variability requires the use of natural proxies (tree rings, sedimentary records) or documentary sources. In this paper we analyse three documentary sources with potential to analyse the long-term variability of droughts: chapter acts, logbooks and chronicles. The chapter acts recorded discussions and decisions made during the assemblies of the local authorities and provide continuous and direct evidence on drought impacts. They are especially useful to study droughts between the 15 and the 19 centuries in Europe and the 17 to 18 in the former colonies. Logbooks recorded the meteorological conditions and the incidents occurred during navigation. They provide indirect information through the circulation indices that can be very helpful to understand the mechanisms and teleconnections associated to droughts. Finally, the chronicles are historiographical documents describing political and social events. They are secondary sources and the references to climatic events are discontinuous, thus their analysis must be extremely careful, but they are especially useful to study specific drought events especially prior to 15th century when no other sources are available. ; Peer Reviewed

Trees, corals, ice cores and documentary evidence provide high-resolution proxies that allow past climate to be reconstructed (Jones et al., 2009). Documentary evidence includes all forms of written historical information about past climate or weather, but its use for climate reconstruction is restricted to locations for which there is a rich documentary legacy. Several climate analyses and reconstructions have been undertaken using documentary evidence from Europe (Brázdil et al., 2005; 2010), North and South America (Dupigny-Giroux and Mock, 2009; Prieto and García-Herrera, 2009; Neukom et al., 2010), Asia (Ge et al., 2005; 2010; Aono and Kazui, 2008; Hirano and Mikami, 2008) and oceanic areas (García-Herrera et al., 2005). The Islamic World is a region for which such sources could also be used to reconstruct past climate, as indeed they have been widely used for astronomy and geophysics. Astronomers have used the observations made by Arab astronomers for centuries, with some remarkable examples. Historical eclipse observations, recorded by various ancient and mediaeval cultures including Arabs, have enabled changes in the Earth's rate of rotation to be monitored with fair precision as far back as around 700 AD (Stephenson, 2003). Rada and Stephenson (1992) catalogued meteor showers using mediaeval Arab chronicles and Ahn (2003) investigated the spatial distribution of meteor streams crossing the orbit of the Earth from the tenth to the fourteenth centuries using chronicles from Korea, Japan, China, Arabia and Europe. Documentary sources from Iberia have been used to identify and date such astronomical phenomena as eclipses and comets (Vernet, 1982), naked-eye sunspots (Vaquero and Gallego, 2002) and aurora sightings (Vaquero and Gallego, 2001). The work of Basurah (2006) provides descriptions for 18 aurora displays on various dates at low latitudes in the Mediterranean area taken from Islamic chronicles (ninth to sixteenth centuries). In seismology, Arabic chronicles were extensively used to prepare the Seismic Catalogue of the Iberian Peninsula (Martínez and Mezcua, 2002) and to study seismic activity in Syria and Palestine (Ambraseseys, 2005). However, the use of these sources to recover climate information is, to the best of our knowledge, still very limited (Bulliet, 2009; Jones et al., 2009). Here we describe a preliminary inquiry based on Arabic documentary sources from Iraq. We would stress the antiquity of the documents used, with dates in the period 816–1009 AD. The sources consulted are Arabic chronicles that narrate the social, political and religious history of different regions in a form very characteristic of Arab culture. ; Peer reviewed

14 Pags.- 5 Figs. Under Creative Commons License CC BY-NC-ND ; 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. ; This work was supported by the research projects CGL2017‐82216‐R and PCI2019‐103631, financed by the Spanish Commission of Science and Technology and Fondo Europeo de Desarrollo Regional (FEDER); CROSSDRO project financed by the AXIS (Assessment of Cross(X)—sectoral climate Impacts and pathways for Sustainable transformation), JPI‐Climate cofunded call of the European Commission and INDECIS which is part of ERA4CS, an ERA‐NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), and ANR (FR) with cofunding by the European Union (Grant 690462). Dhais Peña‐Angulo received a "Juan de la Cierva" postdoctoral contract (FJCI‐2017‐33652 from Spanish Ministry of Economy and Competitiveness, MEC). ; Peer reviewed

International audience ; Drought monitoring is essential to determine, at short time intervals, the main characteristics of drought events, such as their duration, severity, and spatial distribution. To ensure that drought monitoring represents a useful tool for governmental plans aimed at preventing or minimizing drought impacts, up-to-date information must be instantaneously accessible and it must provide high spatial and temporal resolution. This study presents a system that allows the automatic tracking of meteorological droughts in the Spanish territory, based on an open and easy-to-use online platform (https://monitordesequia.csic.es/monitor). This drought monitoring system provides two drought synthetic indices: the Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI). Information is provided on a quasi-weekly basis, in a grid format, with a spatial resolution of 1.1*1.1 km, and with data from 1961 to the present time. This drought monitor is updated based on the real-time information gathered from automatic stations, which in turn requires historic information to identify and track drought events. The drought indices are obtained from data processing (quality control, temporal series reconstruction, homogenisation, interpolation, and validation) using climatic variables (maximum and minimum temperatures, solar radiation, rainfall, dew point, and wind speed) which are provided by the Spanish Meteorology Agency and the Ministry of Agriculture of the Spanish Government. We performed a validation of the drought indices for the whole historical period (1961-2020). This allowed us to observe a strong spatial agreement between the indices obtained with the historical dataset and the indices from the monitoring dataset, especially for mainland Spain and the Balearic Islands (Pearson's r, SPI and SPEI >0.99). The presented real-time drought monitoring system represents a relevant and useful tool that allows for quick and effective actions to prevent and ...

19 Pags.- 5 Figs.- 2 Tabls. © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license ; Drought monitoring is essential to determine, at short time intervals, the main characteristics of drought events, such as their duration, severity, and spatial distribution. To ensure that drought monitoring represents a useful tool for governmental plans aimed at preventing or minimizing drought impacts, up-to-date information must be instantaneously accessible and it must provide high spatial and temporal resolution. This study presents a system that allows the automatic tracking of meteorological droughts in the Spanish territory, based on an open and easy-to-use online platform (https://monitordesequia.csic.es/monitor). This drought monitoring system provides two drought synthetic indices: the Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI). Information is provided on a quasi-weekly basis, in a grid format, with a spatial resolution of 1.1*1.1 km, and with data from 1961 to the present time. This drought monitor is updated based on the real-time information gathered from automatic stations, which in turn requires historic information to identify and track drought events. The drought indices are obtained from data processing (quality control, temporal series reconstruction, homogenisation, interpolation, and validation) using climatic variables (maximum and minimum temperatures, solar radiation, rainfall, dew point, and wind speed) which are provided by the Spanish Meteorology Agency and the Ministry of Agriculture of the Spanish Government. We performed a validation of the drought indices for the whole historical period (1961–2020). This allowed us to observe a strong spatial agreement between the indices obtained with the historical dataset and the indices from the monitoring dataset, especially for mainland Spain and the Balearic Islands (Pearson's r, SPI and SPEI >0.99). The presented real-time drought monitoring system represents a relevant and useful tool that allows for quick and effective actions to prevent and mitigate the effects of drought on society and ecosystems. ; This work was supported by projects PCI2019-103631 financed by the Spanish Ministry of Science and Technology and FEDER and CROSSDRO project funded by AXIS (Assessment of Cross (X) - sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission. ; Peer reviewed

11 Pags.- 1 Tabl.- 4 Figs. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. ; 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. ; This work was supported by the research projects CGL2017-82216-R, CGL2017-83866-C3-3-R and PCI2019-103631, financed by the Spanish Commission of Science and Technology and FEDER; CROSSDRO project financed by the AXIS (Assessment of Cross(X)—sectoral climate Impacts and pathways for Sustainable transformation), JPI-Climate co-funded call of the European Commission and INDECIS which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462). Dhais Peña-Angulo received a 'Juan de la Cierva' postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Conor Murphy was supported by the Irish Environmental Protection Agency (Grant Nos. 2019-CCRP-MS.60). Marco Turco has received funding from the Spanish Ministry of Science, Innovation and Universities through the project PREDFIRE (RTI2018-099711-J-I00), which is co-financed with the European Regional Development Fund (ERDF/FEDER). ; Peer reviewed

This study links tree-ring growth and gross primary production for a variety of forest types under different environmental conditions across Spain. NOAA-AVHRR satellite imagery data were combined with dendrochronological records and climate data at a fine spatial resolution (1.21 km2) to analyze the interannual variability of tree-ring growth and vegetation activity for different forest biomes from 1981 to 2015. Specifically, we assessed the links between tree-ring width indices (TRWi), the Normalized Difference Vegetation Index (NDVI) and a variety of environmental conditions, represented by climatic variables (air temperature, precipitation, evapotranspiration and water balance) and elevation. The impact of these variables on tree growth was assessed by means of the Predictive Discriminant Analysis (PDA). Results reveal a general positive and significant relationship between inter-annual variability of the NDVI at a high spatial resolution (1.21 km2) and tree-ring growth. Maximum correlations between NDVI and tree-ring growth were recorded when cumulative NDVI values were considered, in some cases covering long time periods (6–10 months), suggesting that tree growth is mainly related to Gross Primary Production (GPP) at annual scale. The relationship between tree-ring growth and inter-annual variability of the NDVI, however, strongly varies between forest types and environmental conditions. ; Research projects CGL2014-52135-C03-01, CGL2015-69186-C2-1-R, CGL2015-69985-R, CGL2013-48843-C2-1-R, AGL2014-53822-C2-1-R, (BFU2010-21451), PCIN-2015-220, CGL2016-81706-REDT, CGL2017-82216-R, Spanish Commission of Science and Technology and FEDER, 1560/2015: Herramientas de monitorización de la vegetación mediante modelización ecohidrológica en parques continentales financed by the Red de Parques Nacionales, IMDROFLOOD, Water Works 2014, co-funded call of the European Commission, CROSSDRO financed by the AXIS (Assessment of Cross(X) – sectorial climate Impacts and pathways for Sustainable transformation) JPI-Climate co-funded call of the European Commission and INDECIS, part of ERA4CS, an ERA-NET initiated by JPI Climate, FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR), co-funding by the European Union (Grant 690462). Spanish Commission of Science and Technology and FEDER, and INDECIS, which is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462), Aragon Regional Government, Spanish Ministry of Economy and Competitiveness, Spanish Ministry of Education, Culture and Sport, IJCI-2015-25845, MINECO-FPDI 2013-16600, FJCI 2016-30121, FEDER funds. Xunta de Galicia (PGIDIT06PXIB502262PR, GRC GI-1809, ROCLIGAL-10MDS291009PR), INIA (RTA2006-00117), and Interreg V-A POCTEFA (CANOPEE, 2014-2020-FEDER funds) projects.