Key as in Table 6.10a
Key as in Table 6.10a
The range of variability of the anomalies of daily P and the raininess indices decreases when types are classified into circulation groups. The range is especially small in the case of the macrorypes of circulation (Tables 6.10a-d, Figure 6.16a-c). It should be remembered, however, that the calculation of the efficiency of P for each group and macrotype was conducted on the basis of a significantly greater number of data than for types. This means that their significance per unit of efficiency is much greater. In the cool seasons of the year (autumn and winter), the maximum efficiency of P in the greater part of the Arctic occurs with macrotypes W and C, and with macrotype E in the warm period. The types, groups, and macrotypes of circulation that bring the most efficient P to particular areas of the Arctic, may be the driest ones in other regions. The efficiency of P for particular groups and macrotypes of circulation undergoes significant changes in the annual course (Figure 6.16a-c). However, we can find many examples where for the whole (or almost the whole) year a particular group or macrotype of circulation brings solely positive or solely negative anomalies. At Danmarkshavn, groups A and W may be listed as examples as they have only negative anomalies for all months, while group G has only positive anomalies for the same period (except for June and October). Western circulation brings less P here than usual, while eastern circulation (except for February and December) brings more. The exceptionally pronounced diversity of the efficiency of P depending on the circulation group may be observed in Hopen. It is at this station that groups A, W, and K bring positive anomalies for almost all the year, while B, G, and D bring negative ones (Figure 6.16a).
Apart form discussing the mean efficiency of P, some attention should be also devoted to extreme daily precipitation. A review of its values demonstrates that throughout the Arctic, the value of daily P may equal its monthly, and sometimes seasonal, total. In areas of intensive cyclonic activity (ATLR, PACR) and in CANSRs maximum daily P occurred in the cool season of the year, while in the remaining Arctic regions, characterised by a significantly
continental climate, it occurred in the warm period. Out of the 10 analysed stations, the highest daily P in winter (49.1 mm) and in spring (46.7 mm) occurred at Hopen with types VII and V, respectively, bringing warm and humid air from a southwesterly direction over this area. In summer and in autumn extreme daily P of 58.8 mm and 127.8 mm respectively, was observed at Coral Harbour A, with the inflow of air masses from the Baffin Bay region with types III and V. Thus, it appears that the highest measured daily P in the Arctic equalled 127.8 mm. This value exceeds mean 40-year autumn P in Coral Harbour A by as much as 40%. In all seasons of the year, the lowest values of maximum daily P in the Arctic were observed at Resolute A, where they oscillated between 4.1 mm in winter and 25.1 mm in summer.
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