Spatio-temporal changes in variability of temperature, precipitation and runoff in Finland during the period 1962-2014

This study assesses spatio-temporal changes in inter-annual variability of temperature, precipitation and runoff for 1962-2014 at sub-basin scale in Finland. The analysis is based on 1) interpolated areal average temperature and total precipitation based on corrected observations, and 2) modelled runoff based on the areal averages, both prepared by the Finnish Environmental Institute (SYKE). Temporal changes in variability were analyzed by constructing moving window median absolute deviation time series at annual and seasonal scales. Sub-basins with similar patterns of temporal variability were identified using principal component analysis and agglomerative hierarchical clustering. Presence of monotonic trends in variability was tested. Distinct areas with similar patterns of statistically significant changes in variability were found. Decreases in temperature variability were found annually, in winter and in summer, respectively in many parts of Finland, the south and the north. Precipitation variability increased in autumn in northern Finland, and decreased annually as well as in winter and spring in northern and central parts of Finland. Runoff variability increased in winter in most parts of Finland and in summer in the central parts, as well as decreased in spring in southern Finland. Findings of this study describes hydro-climatic variability in Nordic conditions and hence potentially improves the possibility to adapt and predict the changes in hydro-climatic conditions, including weather extremes.