Long-term temperature changes in Sicily, Southern Italy

Temperature series recorded at 84 measurement stations across Sicily (Italy) have been analysed in order to detect statistically significant changes during the 1924-2013 period. The occurrence of abrupt change points in annual maximum, minimum, and mean temperatures and temperature range series was investigated using cumulative sum (CUSUM) charts. Then, the non-parametric Mann-Kendall test was applied to the average annual, monthly and seasonal series. Prior to the application of the Mann -Kendall test, gaps in the historical dataset were filled using a geostatistical technique, namely the Residual Ordinary Kriging, and then processed to remove the influence of serial correlation on test results. Significant trends were quantified using a robust non-parametric estimate. Once the trends at each site were identified, the spatial patterns in those trends were obtained using the Inverse Distance Weighted. Results indicated a general increase in the analysed series over the area of study. Upward trends in maximum temperatures frequently occurred during the winter months, with the largest increases in the south-west, while mean temperatures increases occurred mostly during the spring, summer and winter. Across a wide western area, a small number of negative trends were observed in annual minimum temperatures, especially in autumn months. Temperature ranges showed both positive and negative trends. Decreasing trends occurred along the eastern coast and in the western part of the region.