Analysis Of A Precipitation Time Series At Monthly Scale Recorded In Molfetta (South Italy) In The Xviii Century (1784-1803) And Comparisons With Present Pluviometric Regime

A time series of monthly precipitation, recorded in Molfetta (south Italy) in the period 1784-1803, was studied in comparison with another analogous series in the period 1977-2015. The old length unit (in royal Paris foot) was converted to the metric system. The two series of 20 and 39 years showed the same mean values of annual precipitation but, after a detailed analysis of the monthly Standardized Precipitation Index (SPI), it resulted that the XVIII century period presented wet to extremely wet seasons in autumn and winter and dry months in summer, with a quite regular alternation of dry and wet years, while 1977-2015 series showed larger seasons of dry to very dry months and shorter wet periods, without any very wet month. The analysis of trends showed that in the period 1784-1803 no clear trend could be identified, while a significant decreasing trend was found in the period 1977-2015. The most recent years, 2012-2015, presented an almost continue series of dry to extreme dry months, with very little precipitation.