NO. 4 TEMPKRATURE VARIATIONS IN THE NORTH ATLANTIC 39 



Islands (Thorshavn) and near the Norwegian coast (Ona and 

 Andenes). 



Prof. Hann (1904-5) has studied the relation between the varia- 

 tions of temperature of northwestern and middle Europe, at Green- 

 wich, Brussels, and \'ienna. A. Buchan had recognized in the 

 year 1867 the dependence between the air-pressure anomalies in 

 Stykkisholm and the air-temperature anomalies over the British 

 Isles. He showed that the cold period in the year 1867 in Scot- 

 land coincided with high air pressure over Iceland and northern 

 Scotland and low air pressure over the channel in southwest Europe, 

 while the great heat of July, 1868, in Scotland coincided with uncom- 

 monly low air jjressure at Stykkisholm and high air pressure over 

 Scotland. The latter correlation occurred also in September, 1865. 

 By investigations over a long period of years, Hann came to the 

 conclusion that " an intensification of the air pressure minimum 

 near Iceland is attended by increase of the winter temperature 

 over northwest and middle Europe, while a diminution of it pro- 

 duces a lowering of the same. In how far the intensity of this 

 North Atlantic barometric minimum depends on the positive or 

 negative temperature anomalies of the ocean water in the North 

 Atlantic is a question which cannot be touched upon in this investi- 

 gation. Such a dependence is in a high degree probable but it is 

 very difficult to recognize and separate the cause and effect in the 

 matter. On one point we may, however, remark. While the 

 anomaly of the ocean temperature is often longer than a whole year 

 of the same sign, the air-pressure anomaly at Iceland varies much 

 oftener. The anomaly of the ocean temperature and that of the 

 air-pressure often dififer in sense." In the summer months he finds 

 the relatio'n between the air pressure in Iceland and the tempera- 

 ture in Europe alternate, as would indeed be expected. 



In this paper Hann investigated also the relation between the 

 variations in the two action centers of the atmosphere over the 

 North Atlantic Ocean. That is to say, he compared the air pressures 

 in the region of minimum near Iceland and the region of high pres- 

 sure near the Azores, and found that in a majority of cases rela- 

 tively lower pressure in Iceland (Stykkisholm) coincided with rela- 

 tively high air pressure in the Azores (Ponta Delgada) . Converselv, 

 low air pressure in Ponta Delgada occurred with relatively high 

 air pressure in Stykkisholm. This dependence, he thinks to ex- 

 plain, at least in part, since a high pressure in the Azores must 

 generally fall with '' an increased activity of the atmospheric cir- 



