Figure 5.34b. Mean annual course of T. anomalies at Hopen and Naryan-Mar taken for the days with groups (A, B, W, G, D, and K) and macrotypes (W, C, and E) of circulation chosen over the periods 1951-1990 (for Hopen) and 1967-1990 (for Naryan-Mar).

Thermal anomalies in Naryan-Mar in all seasons (except for the spring) are higher than in Jan Mayen (Tables 5.20a-d, Figures 5.34a and b). This means that changes in circulation lead to greater thermal changes in Naryan-Mar. In the spring and autumn, the warmest air is brought by group A (anomalies amount to 1.5°C and 2.2°C respectively), in the winter by group W (2.0°C), and in the summer by group K (2.8°C). Decidedly the coldest air masses flow in with group B. Negative anomalies occur in all months and in February they amount to almost-9°C (Figure 5.34b). Circulation macrotype E is the warmest throughout the year (except for May) whereas macrotype C is the coldest (except for July).

The instability of T. of circulation groups and macrotypes is almost twice as high in this area as it is in Jan Mayen. This is caused by Naryan-Mar being located on the continent but in close proximity to the Barents Sea. This determines the alternating inflow of air masses characterised by varied thermal conditions when circulation changes. The thermally uniform maritime region of Jan Mayen, on the other hand, is conducive to a reduction in the thermal differences of the air masses inflowing over this area. The standard deviations computed for Naryan-Mar are highest in the winter (oscillating between 8.9°C and 10.8°C), and lowest in the summer (4.9-5.9°C) (Tables 5.21a and 5.21b).

The northern sub-region. A characteristic feature of this sub-region is, first and foremost, the exceptionally low thermal differentiation occurring in the summer, especially with particular circulation groups and macrotypes (the differences between anomalies do not exceed 0.7°C). In the winter, circulation differentiates T. to the same degree as in other areas of ATLR. In the cold half-year, the lowest 2"., according to their mean seasonal anomalies (Tables 5.20a-d) occur with group B, whereas in the warm half-year they occur most often with group W. Throughout the year, except for the spring, the highest T. in Hopen are noted during the synoptic processes belonging with group K, which are characterised by low-pressure centres occurring south of this station. In such a situation, the warm air from the south flows into ATLSRn along the eastern side of the low pressure centres.

In all seasons, the strongest cooling is brought to this area by the western zonal circulation (W). This is particularly evident in the first part of the year because in the second part of the year circulation C also brings only marginally warmer air. Decidedly the warmest, however, is circulation macrotype E, which causes positive anomalies in each month (Figure 5.34b).

In the summer, ATLSRn is characterised by the most stable thermal conditions of all the Arctic regions (a = 2.10C). In the spring and autumn, it gives precedence in this aspect only to Jan Mayen whereas in the winter the variability of T. is very high (a = 8.4°C), lower only than that observed in Naryan-Mar.

The eastern sub-region. In Ostrov Dikson, which represents this subregion, the greatest changes in T in the cold half-year occur when circulation changes from group A to B or vice versa. The former change brings the warmest air (positive anomalies much above 2°C) and the latter brings the coldest air (anomalies oscillating from -2°C to -6°C). The changes in the remaining circulation groups cause much smaller oscillations of T. (Figure 5.34c).

The course of their annual anomalies is highly differentiated with particular circulation macrotypes (Figure 5.34c). In the autumn and winter, the warmest macrotype is E, in the spring, it is macrotype C, and in the summer - W (Tables 5.20a-d). Macrotype C is the coldest in the autumn, winter, and summer. In the summer, the same anomaly (-0.2°C) is produced also by macrotype E. In ATLSRe in the spring, it is the coldest during operation ofthe western circulation.

In the spring and autumn, ATLSRe is characterised by the greatest instability of T in ATLR(a amounted to 8.8°C and 10.1°C respectively). More variable T in the summer were noted only in Naryan-Mar while in the winter they also occurred in ATLSRn (Hopen). Circulation groups B and K, which in transient seasons bring the most unstable thermal conditions, are characterised by a noticeably lower changeability of those conditions in the winter. In the summer, the lowest were computed for group B (3.5°C) and the highest for K (4.7°C) (Tables 5.21a and 5.21b).

The Siberian Region

This region, represented by the Chokurdakh station, is marked in the course of the year by a high variability of thermal characterisations of circulation groups and macrotypes (Figure 5.34c). A somewhat clearer picture can be obtained through the analysis of mean seasonal anomalies ofT. (Tables 5.20a-d). In the winter, it is the warmest with group B, which produces a positive anomaly 1.8°C. The remaining groups are characterised by negative deviations from the norm. In the spring and autumn, the warmest group is G (anomalies amount to 3.8°C and 4.0°C respectively) and the coldest is W (-4.1°C and -3.1°C). In the summer, the highest anomalies are caused by group D (1.3°C) whereas the lowest are brought by groups B (-1.1°C) and K (-1.0°C).

In connection with meridional circulation macrotypes, the warmest air inflows over the area analysed almost all year. In the winter and spring, the highest anomalies characterise macrotype C (0.5 °C and 1.6°C) and in the summer and autumn - macrotype E (0.1°C and 0.9°C) (Tables 5.20a-d, Figure 5.34c).

SIBR in the spring and autumn is characterised by the highest instability of T. of regions of the Arctic. Mean a amounted there to 11.1°C and 12.8°C respectively. A higher variability of in the summer is observed only in the eastern part of ATLSRs. In the winter, this area is characterised by a high stability of T. (Tables 5.21a and b). This is caused by the fact that in this season the thermal conditions of the continent of Asia, which surrounds Chokurdakh, are similar to those of the Arctic Ocean (cf. Figure 5.1).

Figure 5.34c. Mean annual course of T. anomalies at Ostrov Dikson and Chokurdakh taken for the days with groups (A, B, W, G, D, and K) and macrotypes (W, C, and E) of circulation chosen over the period 1967-1990.

The Pacific Region

The thermal differentiation of particular circulation groups is the highest in the spring and autumn and the lowest in the summer (Tables 5.20a-d, Figure 5.34d). As a result, the greatest instability of T. is noted in these seasons (a amounting to 9.7°C and 8.8°C respectively), similar to SIBR. In the winter, the highest thermal anomalies were observed with circulation group B (1.9°C) and in the remaining seasons they are most often observed with group G. In PACR, it is coldest during the domination of group W, which is characterised by the development of anticyclonic activity in this part of the Arctic.

In the winter, the warmest air flows into PACR in connection with the zonal circulation; in the spring and summer, this happens with macrotype C, and in the autumn - with macrotype E. The decrease of T. below the norm in the winter is brought about by macrotype E (by 0.6°C), in the spring and summer by W (by 1.2°C and 0.0°C respectively), and in the autumn by C and W (by 0.7°C) - (Tables 5.20a-d, Figure 5.34d). The magnitudes of standard deviations of T. with particular circulation groups and macrotypes in this region are among the highest in the Arctic (Tables 5.21a and b). Both in the winter and summer, the greatest instability of T. accompanies groups G and K, whereas the lowest instability accompanies group W. It is similar in the spring, except that group A is also characterised by high a. The situation, however, looks different in the autumn. Group W is characterised by the highest o and group D by the lowest a.

The Canadian Region

An analysis of the data from Tables 5.20a-d and Figures 5.34d and 5.34e demonstrates that the thermal characteristics of particular circulation groups and macrotypes are highly similar in both the sub-regions (CANSRs and CANSRn). In the winter, the warmest circulation group B produces positive anomalies of T., amounting to l.FC in CANSRn and to 1.2°C in CANSRs. In the former subregion, the lowest anomalies are caused by group W (-0.7°C) and in the latter, by group G (-1.4°C). Negative deviations of T. from the norm occur in CANR during the operation of macrotype C whereas positive ones in the north accompany macrotype W and in the south - macrotype E (Table 5.20a).

The spring and the autumn are the warmest when circulation group G is active. It is worth adding that this group in both seasons is characterised by positive anomalies throughout the Arctic. The greatest negative anomalies (ca. -3°C in the spring and ca. -2°C in the autumn) accompany group W, which produces negative deviations of T. from the long-term mean throughout the whole area of the Arctic, except for the eastern part of ATLR. In the spring, its highest values accompany macrotype C whereas the lowest accompany macrotype W. In the autumn, in turn, the warmest air is brought by the zonal circulation whereas macrotype E brings the coldest air (anomalies amount to 0.4°C and -0.4°C respectively) (Table 5.20d).

Figure 5.34d. Mean annual course of T. anomalies at Mys Shmidta and Resolute A taken for the days with groups (A, B, W, G, D, and K) and macrotypes (W, C, and E) of circulation chosen over the period 1967-1990 (for Mys Shmidta) and 1951-1990 (for Resolute A).

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