Historical agricultural droughts from the INternational Pro pluvia ROgation database

We present the INPRO (INternational Pro pluvia ROgation) database, the first international initiative to compile and share information on pro pluvia rogation ceremonies. Rogations are religious rites celebrated in supplication to gods for changing the environmental or social risks brought to their communities. Pro pluvial rogations have the specific objective to obtain rainfall during drought periods. This proxy has been used to understand drought variability in the pre-instrumental period, to generate precipitation or atmospheric circulation modes reconstructions, to validate natural proxies, or to understand the social consequences of droughts, mainly during the last 500 years. Different methodologies have been used in the literature to extract the climate signal from this proxy. Here, we evaluate the pros and cons of these methodologies, with special attention on methodologies based on the date of the celebration, since it is the main variable provided by INPRO. Important questions to take advantage of INPRO database are discussed e.g. types of documentary sources (primary or secondary), time resolution (daily, monthly, seasonally or yearly) or seasonality (related with agricultural labours). Finally, we provide recommendations for the use of IMPRO depending on the different research objectives e.g. case studies, drought reconstruction, proxies validation. Currently INPRO database has more than 3500 dates of pro pluvia ceremonies in 153 locations of 11 countries (Mexico, Guatemala, Ecuador, Peru, Chile, Argentina, Portugal, Spain, France, Italy, Philippines). The database covers the period from 1333 to 1949, being the 18^th century when more information is available. INPRO database can be freely accessed and visualized via http://inpro.unizar.es/.