Local recent changes in extreme air temperature

Daily minimum and maximum air temperatures recorded in Naples (1872–1982) and in surrounding areas have been analysed in order to set up a statistical model for investigating climatic changes of extreme air temperature. We have analysed on various time-scales the mean values of minimum air temperature lower than the 10th percentile (Tmin₁₀) and the mean values of the maximum air temperature greater than the 90th percentile (Tmax₉₀). The results have shown for the city: (i) a significant secular trend both for yearly Tmin₁₀ and Tmax₉₀, mostly due to the process of urbanization, that is also responsible for (ii) the ascertained change in the character of the annual cycle, (iii) a reasonable ability to forecast winter Tmin₁₀ and summer Tmax₉₀ in statistical terms using a markovian model, and (iv) a significant 11-yr cycle with an amplitude of 0.5 °C directly related to solar activity which has never been succesfully determined before.