Reconstructing Historical Droughts in Spain (1806–1865): Atmospheric Dynamics versus Qualitative Impact Records

Significant droughts occurred during the 19th century in the Iberian Peninsula causing severe social and economic consequences.  Such events are typically studied through quantitative indices like the Standardized Precipitation Index (SPI); however, in this case study, instrumental rainfall data only reliably cover the last thirty years of the century.  The limited spatial coverage of these early instrumental data justifies the use of historical documentary sources for the study of droughts during this transitional century between the purely pre-instrumental period and the modern instrumental era. In this work, we developed drought indices based on rogation ceremonies from municipal documentary sources compiled in the AMARNA^® Platform (Multidisciplinary Archives for Analysis of Natural and Anthropogenic Risk) and analyzed two atmospheric indicators from the 20CRv3 reanalysis: sea-level pressure and geopotential height at 500 hPa.

The results show a decrease in the sensitivity of historical drought records starting in the mid-19th century, likely due to social and political changes. Additionally, although historical data on drought impacts are mainly documented during late winter and spring, critical seasons for harvests, the atmospheric configurations likely conducive to droughts occurred predominantly during the winter prior to the social response. The complexities of historical data, such as the delays between the onset of a meteorological drought and the documentation of its impacts, combined with the inherent physical propagation of water deficits through natural systems, underscore the necessity of considering time lags when studying historical climate phenomena.

The nineteenth century presents distinct difficulties for drought reconstruction. This is not only because of the decline in civil administrative sources recording drought rogation ceremonies but also because it corresponds to the early stage of institutional meteorological records, which are characterized by a limited number of observation points and still-developing methodologies. Despite these challenges, the availability of reanalysis data opens new avenues for the study of a period highly relevant period for understanding drought behavior from a historical perspective. At the same time, the historical data used in AMARNA do not encompass all the documentary sources available in Spain. Fortunately, Spain’s documentary heritage offers considerable potential for further research through both supra-municipal and ecclesiastical administrative records. 

The authors acknowledge the grants from FLOODMED (PID2024-157662OB-C22), funded by the Spanish Ministry of Science, Innovation and Universities (MICIU/AEI/10.13039/501100011033) and by ERDF/EU.