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 × 10 km 2 ) 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 .