Interannual variations and trends in surface air temperature in Finland in relation to atmospheric circulation patterns, 1961-2011

• Annual and seasonal variations in surface air temperature (SAT) during the period 1961–2011 were analysed using daily mean temperature data sets from regular grid points (10×10km2) throughout Finland. The Mann–Kendall nonparametric test was used to detect significant historical trends in SAT and Spearman's correlation coefficient (ρ) to test the relationships between SAT patterns and various atmospheric circulation patterns over the northern hemisphere. The results showed that mean annual SAT in Finland increased (p<0.05) by 0.4±0.2°C per decade during the study period and that the SAT was significantly (ρ=0.58, p<0.05) positively correlated with the Arctic Oscillation (AO) index. However, there were spatial differences within Finland for both the trends and relationships with the atmospheric circulation. Analysis of seasonal mean SAT identified significant (p<0.05) warming trends for both spring (by 0.4±0.2°C per decade) and summer (by 0.3±0.2°C per decade). Winter and spring mean SATs were most strongly (p<0.05) correlated with the AO index (ρ=0.72 and 0.42, respectively), while the most significant teleconnection pattern for mean SAT in summer was the East Atlantic (EA) pattern (ρ=0.43, p<0.05); and in autumn the EA/West Russia (WR) pattern (ρ=−0.59, p<0.05). These results provide a detailed spatial picture of climate warming in Finland in recent decades and reveal that interannual variation of the SAT in Finland is closely linked with a number of atmospheric circulation patterns, not just the AO and North Atlantic Oscillation (NAO). Annual and cold-season SAT are mainly influenced by the AO and NAO, whereas the EA, EA/WR, Scandinavia (SCA) and West Pacific (WP) patterns play an important role for warm-season SAT.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences (hsv//eng)

Nyckelord

interannual variability;trend analysis;surface air temperature;Finland;atmospheric circulation patterns

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