Rainfall is one of the basic climate variables. Variability of the rainfall has a great impact on disciplines related to water (e.g., farming, hydropower, construction etc.). Identification of rainfall trend is important for understanding of the climate change or variability impact and detecting the factors, which cause changes in rainfall characteristics.
Diploma thesis consists of statistical analysis of rainfall, which includes the presentation of maximum, minimum and quartile of monthly rainfall sum, graphic presentation of average monthly rainfall, histogram of daily rainfall and the graph of annual rainfall with linear trend line. The statistical analysis is carried out using software R and includes 20 rainfall and meteorological stations in Slovenia for the period 1970-2017. Furthermore, for the selected stations the Mann-Kendall test of the monthly and yearly maximum trend and yearly rainfall trend is performed. Additionally, the seasonality analysis of daily maximum amounts of precipitation was conducted.
The results of analysis indicate that monthly and annual precipitation amounts show an increasing trend, however the detected trend is statistically insignificant with selected significance level of 0,1 for almost all stations. Mann-Kendall's trend test was also performed for days without precipitation (i.e. dry days). It was found that the dry days trend for most stations is increasing and statistically insignificant with the selected significance level of 0,1. In order to determine the influence of the stations geographical location on the amount of precipitation, the analysis of the dependence of annual rainfall amounts to the altitude and distance from the sea was investigated. The variability of the rainfall amount and obtained trend results are probably consequence of the strong natural geographic diversity of Slovenia. It was found that some degree of seasonality exists for all analyzed stations, and seasonality is most significant for the Polički Vrh station. The results of the seasonal analysis showed that the highest annual maximum daily precipitation was detected during the summer and autumn, which suggests that a large part of Slovenia has continental climate characteristics.