The role of atmospheric circulation patterns in agroclimate variability in finland, 1961–2011

Abstract

This study evaluates interannual variations and trends in growing season daily temperature sum and daily precipitation sum in Finland during 1961-2011, and their connections to well known atmospheric circulation patterns. Changes in summer (June-August) climate partially explain changes in growing season daily temperature sum and daily precipitation sum over Finland, which naturally decreased from south to north. On a national scale, growing season warmed and became wetter during 1961-2011, as growing season daily temperature sum and daily precipitation sum significantly (p < 0.05) increased by 5.01 ± 3.17°C year -1 and 1.39 ± 0.91 mm year -1 , respectively. The East Atlantic pattern was the most influential atmospheric circulation pattern for variations in growing season daily temperature sum (rho = 0.40) across Finland and the East Atlantic/West Russia pattern was most influential for growing season daily precipitation sum variability (rho = -0.54). There were significant (p < 0.05) increasing trends in growing season daily temperature sum and daily precipitation sum throughout Finland during 1961-2011. Increased growing season daily temperature sum was mainly observed in northern, central, western, eastern and coastal areas of south-western Finland. This warming was positively associated with the East Atlantic pattern in the north, centre and south, but negatively associated with the East Atlantic/West Russia pattern in eastern Finland. Increased GSP mostly occurred in southern, eastern, western, central, northern and north-western Finland. These wetting trends were positively correlated with the East Atlantic pattern in the north and negatively correlated with the Polar pattern in the south and the East Atlantic/West Russia pattern in the east, west, centre and north-east of Finland. The overall agroclimatic year-to-year variability in Finland between 1961 and 2011 was mostly linked to variations in the East Atlantic and East Atlantic/West Russia patterns.

Analysing the variability and trends of precipitation extremes in Finland and their connection to atmospheric circulation patterns

“…Alexander et al, 2006;Klok and Klein Tank, 2009;Irannezhad et al, 2014). In contrast, Irannezhad et al (2016a) concluded decreasing trends in very light precipitation in Finland during 1908-2008. They also reported decreases in wet day precipitation and SDII in central Finland.…”

“…Similarly, Casanueva et al (2011) reported significant relationships between the SCA pattern and the wet spells over Europe. Similar to the results obtained by the present study, Jaagus (2009) and Irannezhad et al (2016a) concluded that the POL pattern is the most influential ACP for variability in extreme precipitation intensity over the south of Finland.…”

“…Similar to the results obtained by the present study, Jaagus () and Irannezhad et al . () concluded that the POL pattern is the most influential ACP for variability in extreme precipitation intensity over the south of Finland. The positive correlations between the EA pattern and precipitation intensity over central Finland identified by this study were previously reported by Irannezhad et al .…”

“…Irannezhad et al . () showed that the EA/WR pattern principally controls daily precipitation intensity, frequency and duration at three meteorological stations in southern, central and northern Finland, particularly during summer season. They also identified that the SCA pattern significantly influences the wet and dry spells over Finland.…”

“…Using 101‐years (1908–2008) precipitation records at three meteorological stations in southern, central and northern Finland, a very recent study by Irannezhad et al . () determined significant decreases in annual sum of very light precipitation, while its number of events increased. It means that very light precipitation in Finland is falling more frequent than before, but with less intensity.…”