Detection of variations in precipitation at different time scales of twentieth century at three locations of Italy

In continuation of efforts to contribute to the studies on climatic change, 120 years time series precipitation of Firenze, Pisa and Palermo of Italy was analyzed over two time scales (10 and 60 years). Within the long (60 years) time scale, patterns of annual, seasonal, and monthly precipitation were studied. Mean annual precipitation decreased by 50, 148 and 84 mm, and annual rainy days decreased by 8, 12 and 3 days respectively, at Firenze, Pisa and Palermo in 2nd half than in 1st half of the century. Precipitation in spring season at Firenze and Pisa and in winter at Palermo showed highly significant decline in 2nd half of the century compared to the 1st half. Decline in rainy days was also higher in spring season (by 4 days per year) at Firenze and Pisa and in winter (by 3 days per year) at Palermo in 2nd half of the century. Monthly precipitation means in 2nd half, however, depicted increase of precipitation across all the three locations (non-significant) only in August and September. Long-term (120 years) trend over 20th century reveals highly significant negative trend in rainy days at Firenze and Pisa and in precipitation at Pisa and Palermo. Most interesting observation from this study is the highly significant increase in the days with low (< 1 mm) precipitation at all the locations and decrease of days of frequently occurring precipitation amounts (5 to 15 mm) by 4 and 6 days per year at Pisa and Palermo, in the later half than in 1st half. Long-term standardized precipitation indices depicted downward trend in precipitation and increase in dry years with longer duration and higher intensity in the later half at all three locations. Decline in the precipitation and rainy days, increased precipitation extremes and intensities noticed in this study are similar to the globally observed signals of Green House Gases induced climate change.