|ABSTRACT||Assessment of existing climate variability and trends is essential for various environmental and climate impact studies and a basis for climate change scenarios preparation. Slovenian Environment Agency has an extensive archive of meteorological measurements which dates back to 1852, when the first instrumental measurements on the territory of Slovenia had been carried out. However, only meteorological data from 1961 onwards were systematically digitised.
For a robust assessment of climate change high-quality climate data is needed. To obtain such data, several important steps should be taken from measurements to data analysis, including quality control and homogenisation. Until 2013 only incomplete attempts, missing intensive homogenisation and quality control procedures, have been made to get a high-quality climate series for Slovenia. To fill the gap, the Slovenian Environment Agency (ARSO) launched the Climate Variability in Slovenia (CVS) project in November of 2008. The aim of the project was to deliver a comprehensive analysis of climate change and variability in Slovenia since 1961.
In the first step time series of daily temperature, precipitation, sunshine duration and air humidity data from Slovenian stations spanning 1961 to 2011 have been rechecked via an intensive quality control procedure. Suspicious values were flagged by computer software and then manually inspected by comparison with the data from the paper archive, data visualisation and automatic spatial comparison. In the same time station metadata was systematically collected from many different sources and digitised. Quality control and metadata revealed the general quality of measurements at each station. Stations with low quality time series were discarded from further procedure. In the second step high quality time series were subject to a homogenisation procedure which was performed by recently developed software package, HOMER (Mestre et al., 2013).
Based on quality controlled and homogenized time series the variability and trends of 7 climate variables were analysed; Air temperature, precipitation, fresh snow depth, accumulated snow depth, sunshine duration, reference evapotranspiration and air pressure. The results are consistent with detected regional trends of climate variables (EEA, 2015). Temperature trend between 0.35 and 0.45 °C/ decade is significant all over the country. On the other hand, precipitation-wise, statisticaly significant decreasing trend is limited to the western part of Slovenia. A significant decrease both in fresh and accumulated snow depth however is detected across the whole country, the highest occuring in mid altitudes. There is an increasing trend in solar radiation, allocated mainly to spring and summer.|