Tirano (1624-1930): a long time series of harvest dates for grapevine

Since Middle Ages, the rulers of many territories of Europe defined grape harvest dates for a lot of motivations, sometimes producing quite long archives of dates. These data are useful for paleoclimatic reconstruction because the date of harvest is influenced by a set of climatic variables like temperature, precipitation, solar radiation and so on. More specifically, the main determinant of grape harvest date is the maximum air temperature of Spring – Summer period. In this work, time series of grape harvest dates (1624-1930) for the Alpine area of Tirano - Valtellina (North Italy) were analyzed by means of a linear model approach to reconstruct maximum temperatures of Sondrio for the bimester May - June. Unavaible data were rebuilt by means of a correlation analysis between harvest dates of Burgundy and Tirano. The final product was represented by a time series of May - June temperatures for the whole period 1624-2003. Some climatological evaluations were carried out; in particular homogeneous periods were defined and characterized adopting a statistical approach founded on a change point analysis.