Change-point analysis of some climate variables in Slovenia

Abstract

When studying observed climate changes it is often important to test stationarity of a given meteorological time series. The classical change-point problem is to test for the existence of a change-point and estimate its location if it exists. The study of climate trend in Slovenia is based on long-term records of air temperature, precipitation, duration of snow-cover, stream-flow and phenological data over the last five decades. For all data sets, the annual and half year time series were computed. The Mann-Whitney-Pettit test was used to test the null hypothesis and to determine the change-point. The results of Mann-Whitney-Pettit test indicate the increase in annual air temperature, the shorter duration of snow cover and earlier flowering of plants after year 1987. Decrease in stream-flow appears at the end of 80s and decrease in precipitation at the end of 60s. We can reject null hypothesis with significance level of a=0.05 and conclude that there was a change in Slovenian climate due to global warming.