Modelling snowfall in southern Italy: a historical perspective in the Benevento Valley (1645-2018)

Abstract

The lack of long-term, homogeneous snowfall records is a limitation in environmental studies. Statistical modelling holds potential to extend snowfall records back in time with a limited set of predictors: snow severity and winter-spring temperatures (with their variability) to reflect elevation influences. The annual number of snow days (SDY) in the Benevento Valley (southern Italy) was detailed for the period 1870-2018. Calibrated in the period 1870-1968 (R2 = 0.85) and validated in the period 1969-2018 (R2 = 0.67), the model developed here enabled the reconstruction of a time-series of SDY between 1645 and 2018. This unique series (the longest in southern Italy) shows that SDY peaked during the Little Ice Age (until ~1850), dominated by cold air masses or characterized by winter seasons extending until May (1655, 1684, 1763 and 1830) or June (1620). After the change-point detected in 1866, the modelled SDY time-series declined rapidly (Modern Warming Period, 1867-2018). The atmospheric conditions that favoured snowfall in the Benevento Valley throughout the study period were generally associated with an anomalous high-pressure system located over northern-northwestern Europe and a low in the eastern Mediterranean. This configuration allowed the incursion of cold continental air from the east-northeast into southern Italy. Our results are consistent with similar studies of snowfall in other European and mid-latitude regions of the northern hemisphere.