Giovan Stefano Conti’s rain records in Lucca (Tuscany, Italy) (23rd September 1744-21st July 1794)

Abstract

During the years that followed the closure of the Accademia del Cimento in Florence, as far as we know now, the meteorological measurements suffered a setback, which lasted until the early eighteenth century, when they revived in various areas of the Country, although with significant geographical discrepancies. In the town of Lucca, Giovan Stefano Conti (7 March 1720-28 March 1791), from 23^rd September 1744 until a few days before his death, collected data concerning rain, atmospheric pressure and air temperature he recorded at the Palazzo “alla Pantera” in the Fillungo of the city; in the following three years the measurements were continued by his brother Carlo, to be ended on 20^th July 1794. The rain, collected into a “jar” with the mouth calibrated to half square Florentine arm, was weighed at the end of each month: the conversion of measurement units used in Lucca in the eighteenth century into decimal units resulted into an average annual value of the rain of 1,290.2 mm, with extreme values ​​of 903.2 mm in 1775 and 1,843.2 mm in 1786. The seasonal regime showed the maximum rainfall in autumn (34.4%), followed by winter (31.5 %), spring (22.6%) and summer (11.5%) (sub-Mediterranean regime). The annual rainfall trend had drought phases, such as in the Mid-Fifties and between the end of the Eighties up to the end of the measures, alternating with wet periods, which affected the Mid-Sixties and Seventies. Overall, the catalog trend is slightly negative (-4.8 mm/10 years). Giovan Stefano Conti’s pluviometric series, free from “non-climatic inhomogeneities”, is therefore suitable for representing the characteristics of rainfall in the second half of the eighteenth century in the town of Lucca. It is a meteorological document of great importance, both for the excellent conservation of the manuscript and for the care with which it was drawn up, but above all for the duration of the measurements and the “observations about the season and state of the weather”. It can be used both for synchronic comparisons, for example with the rain recorded in Camaiore by Pietrantonio Butori, for the overlapping sections of the two catalogues from 1777 and 1793, and for the diachronic comparison with the rain recorded at the Botanical Garden of Lucca in the last fifty years. Such analysis offers a significant contribution to the current discussion about the trend of rainfall in Tuscany, which too often seems to be totally devoid of historical perspective.