The first decade of the study period was characterised by relatively low fluctuation of air temperature in Central and Eastern Europe. No ECS was recorded and there was only one EHS, which was only recorded at a single station (Kossowska-Cezak and Twardosz 2012, 2013a, b). There were only two ECMs.
There were two ECSs during each of the following two decades. During the 1960s, exceptionally cool summers were observed in 1962 and 1969.
The ECS of 1962 was one of the two most widespread ones, as it covered 11 stations stretching from Finland, to lands east of the Baltic Sea and to north-western Russia with Smolensk, Moscow and Kostroma (Fig. 4). This was also the coolest summer of the 60-year period. The average temperature was lower than the respective long-term average by 2–3 °C (average temperature anomaly Δt from −2.0 to 3.7 °C). All months of the summer were cool, including an ECM in June in Latvia and Estonia. Elsewhere June or July was the coolest of the study period, but not to the point of being ECM. There were no hot days or tropical nights anywhere but only individual summer days (e.g. two in Moscow compared to 27 on average; and three in St. Petersburg compared to 16; Table 5). During this summer, especially in June and July, northern circulation clearly dominated (Sidorenkov and Orlov 2008).
Table 5 Thermal characteristics of the summer of 1962, 1969, 1976, 1978, 1984 and 1994 (1) and long-term average (1951–2010) (2)
The ECS of 1969 covered north-eastern Russia from the White Sea to Ivdel’ and Perm, but excluding Pecora (where it was still one of the two coolest summers) (Fig. 4). At most of the stations, this was the coolest summer of the study period (Table 5) and June was an ECM. In June, the anomaly achieved a record 5.5 °C and 5.3 °C, respectively, at Syktyvar and Pecora. The average temperature anomaly (Δt) of this ECS ranged from −2.4 °C to −2.9 °C. Summer days were sporadic (7 in Arhangel’sk and 8 in Perm, compared to 15 and 29 on average, respectively).
The 1970s were marked by two vast ECSs and two ECMs with exceptionally low temperatures and also a large coverage. The ECS of 1976 was recorded in two distinct areas. The larger of them was a long “tongue” stretching from eastern Finland and north-eastern Russia, to St. Petersburg, Moscow, Tambov and to Kharkiv in north-eastern Ukraine (Fig. 4). The other one was smaller and covered some of the south-western edge of Ukraine and central Romania up to its southern border. The temperature anomalies of both ECSs were similar at −2.1 °C to −3.1 °C. The −3.1 °C anomaly at Voronez and Tambov was the greatest negative summer anomaly in this study. At nearly all stations of the two areas, this was the coolest summer of the study period (Table 5). All summer months were cool, including an ECM in June in St. Petersburg and August in Chernivtsi and Bucuresti. At each of the stations one of the months, mostly August was the coolest of the study period. Summer days were observed everywhere, but were much fewer than on average (by ca. 1/3rd, e.g. 5 in St. Petersburg, 16 in Tambov, compared to an average of 16 and 45, respectively). Hot days were only recorded in Bucuresti (6 vs. 34 on average).
As has already been mentioned, August was a very cool month. Indeed, it was an ECM from the south-western tip of the area all the way to the Black Sea coast. It was the coolest August of the study period with an anomaly ranging from −3.1 °C to −4.0 °C. Summer days were rare and Odesa experienced none (19 on average), marking it as the only August without summer days during the 60 years and one of two such months overall.
The summer of 1978 was cool across the entire area of Central and Eastern Europe, but was classified as an ECS (t ≤ tav.− 2σ) in three distinct areas: in the southwest, excluding its south-western tip; in the northeast, excluding Pecora; and along the lower Volga river valley (Fig. 5), covering the largest number of 13 stations in the study period. Throughout the rest of the study area, the anomaly was just short of the criterion adopted. At nearly all the stations, this was the coolest summer of the period (Table 5) with an anomaly Δt from −1.9 °C to −2.9 °C. At some of the stations, June or July was an ECM. Summer days were observed at all stations, but less often than normally (e.g. 13 vs. 29 in Perm, 10 vs. 28 in L’viv and 73 vs. 85 in Astrachan’). Hot days were only recorded in Astrachan’ (29 vs. 52), as were tropical nights (11 vs. 26). Based on an analysis of the Met Office synoptic maps of Europe, it was established that the entire summer of 1978 was dominated by western and northern circulations with a high frequency of cyclonic situations.
During the 1970s, the ECM in July 1979 covered a particularly large area. It included Lithuania, Latvia, eastern Poland and Belarus, western Ukraine and Romania. This was the coolest July of the study period with an anomaly ranging from −2.7 °C to −4.0 °C. Summer days were only recorded in the south of the area and two hot days occurred in Bucuresti (14 on average).
During the 1980s, there was just one ECS that cleared the 5 % threshold. It was limited to central and eastern Romania and an adjacent eastern tip of the Ukraine, as well as Moldova. The Δt ranged from −2.1 °C to −2.3 °C. June or July achieved the status of ECM at some of the stations. Both hot and, in the far southern section of the area, very hot days were recorded, but less frequently than on average (10 hot days in Bucuresti compared to 34 on average, see Table 4).
The last decade of the twentieth century also had one ECS clearing the 5 % threshold in 1994. It covered an area including the three south-eastern stations of Ural’sk, Orenburg and Aktobe. This was the coolest summer of the study period at these stations (Δt −2.5 °C to −2.8 °C) with July being the coolest ECM of the period. Summer and hot days were recorded, but much less frequently than on average (35 and 5 vs. 65 and 30 in Orenburg; Table 5).
During the first decade of the twenty-first century, there were no ECSs in the area and even an ECM was very rare (2, exactly the same as in the 1990s). However, June 2003 was classified as an ECM, and it was the most widespread ECM of the entire study period. It stretched from the White Sea coast towards the southeast through Moscow and Niznij Novgorod to western Kazakhstan and was the coolest June of the study period in the area. The average temperature was lower than the long-term average by between 3.7 °C and 5.0 °C. The −5 °C anomaly of the average monthly temperature in Ural’sk was among the greatest anomalies across the period. (There were only seven cases of an anomaly equal to or greater than −5 °C among the 117 cases in the study; the greatest value of −5.7 °C was recorded in Pecora in July 1997). Interestingly, this exceptionally cool June in 2003 was also exceptionally hot (and the hottest in the study period) in Western Europe, including in the south-western tip of the study area (e.g. the anomalies of +4 °C in Vienna and +4.6 °C in Zagreb).