Air temperature and precipitation analyses on a small Mediterranean island: the case of the remote island of Lastovo (Adriatic Sea, Croatia)

Abstract

The paper analyses a series of annual, monthly, and daily air temperatures, and annual and monthly precipitation at the Lastovo meteorological station on the island of Lastovo (Croatia) during the 1948-2018 period. The small carbonate Adriatic island of Lastovo is the most remote inhabited island in the Croatian part of the Adriatic Sea. The absolute minimum annual air temperatures range between -6.8 °C (recorded in 1963) and 4.0 °C (recorded in 1974), with an average value of -1.2 °C. The Mean annual air temperatures range between 14.7 °C (recorded in 1980) and 17.4 °C (recorded in 2018), with an average value of 15.8 °C. The absolute maximum annual air temperatures range between 31.7 °C (recorded in 1959) and 38.3 °C (recorded in 1998), with an average value of 34.8 °C. A strong jump in the minimum annual temperatures started in 1972. The mean annual temperature jump began nine years later in 1981, while the maximum annual temperature jump occurred in 1992. The values of the t-test for all three analysed annual temperature indices (ATI) substantiate the conclusion that the average values in two subperiods defined by the RAPS method are statistically significant at the level p<<0.01. The increasing trend of air temperatures is significantly higher for the time series of the average maximum temperature Tmax than for the time series of the average minimum temperature Tmin. The most prominent increasing trend occurs in June and July. The number of warm and hot days in Lastovo has continuously increased over the analysed period. The increasing trends for both indices are statistically significant at the level p<0.01. The day-to-day (DTD) method established a decrease in the night-time to night-time variability, and an increase in the day-time to day-time temperature variability. The number of frost days is steadily decreasing. The average annual precipitation in the 1948-2018 period was 666 mm, while the minimum and the maximum precipitation was 368 mm and 1089 mm, respectively. No trends have been established for the annual and the monthly precipitation time-series during the 1948-2018 period, though a statistically insignificant drop in annual precipitation is found after 1982.