Spatio-temporal hydro-climate variability in Finland

• Main Author: Lindgren, Ville
• Other Authors: Räsänen, Timo, Guillaume, Joseph, Insinööritieteiden korkeakoulu, Kummu, Matti, Aalto-yliopisto, Aalto University
• Format: Master Thesis
• Language: English
• Published: 2016
• Subjects: climate change; climate variability; hydro-climate; temperature; runoff; Northern Finland
• Online Access: https://aaltodoc.aalto.fi/handle/123456789/23929

The climate in Finland is changing – temperature and precipitation are increasing, resulting in varying runoff patterns. These hydro-climatic trends have been well studied previously, but the changes in variability are less known, despite their importance for understanding climate change. This research aims to assess spatio-temporal changes in variability of temperature, precipitation and runoff for the years 1962-2014 at sub-basin scale in Finland. Temporal changes in variability were analyzed by constructing moving window median absolute deviation (MAD) time series at both annual and seasonal scales. Areas with similar patterns of variability were then identified using principal component analysis (PCA) and agglomerative hierarchical clustering. Direction and statistical significance of changes in MAD were studied using a test for a monotonic trend in variances. Distinct areas with similar patterns of statistically significant change in variability were found. With regard to temperature, this study found decreases in annual and winter variability in most parts of Finland, as well as summer variability in northern Finland. In terms of precipitation, decreases were identified for annual variability in the south of Finland, for spring variability in the central part of the study area and for autumn variability in southeastern Finland, as well as increases for autumn variability in northern Finland. For runoff, variability increased in winter in most parts of the study area and in summer in the central part of the study area, as well as decreased in spring in southern Finland. Comparison with previous studies illustrates how trends in mean climate and its variability do not necessarily match; both aspects need investigation. Findings of this study provide new information on hydro-climatic variability in Finland and improve the possibility to adapt and predict the changes in hydro-climatic conditions, including intensity and frequency of weather extremes. Suomen ilmasto muuttuu – lämpötila ja sadanta kasvavat, ja ...