NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC 1 9 



•The cloudiness varies in February along the steamer route from 

 the Channel to New York on the average between 6.5 and 7.8 on a 

 scale of 10. In the southeasterly part of the investigated region 

 (Portugal- Azores) the cloudiness diminishes from 7 at the north- 

 west to 5-4 in the southeast on the coast of Portugal. 



The frequency of precipitation in February has an average value 

 during the whole interval covered by the observations between 10 

 and 20 per cent along the northerly steamship route, and between 

 5 and 18 per cent in the southern part of the investigated region. 

 It is greatest in the northwestern and least in the southeastern por- 

 tion of the region. In March both cloudiness and frequency of 

 precipitation is somewhat less than in February. 



The average temperature conditions in February and March- 

 April, as we have found them for the eleven-year period 1900 to 

 1910 along the steamer pathway Channel-New York, are given in 

 figure 10. The curves on this figure are based upon the mean 

 values for our chosen 2° fields shown by cross-hatching in figure i 

 and plate 15. In regions where two such fields adjoin one another 

 in a north and south direction, we have given the mean value in 

 our curves. In figure 10 the results for the three February decades 

 are indicated by a full line and those of the second decade group 

 (March 15 to April 13) by a dotted line. The curves " W " cor- 

 respond to the surface temperatures " L " to the air temperatures, 

 and " W-L " to the difference between the two. As the reader will 

 see, the surface temperatures show a somewhat general increase 

 from the east toward the west up to an absolute maximum about 

 44° west longitude of approximately 14.7° C. for both decade 

 groups. From there the temperature sinks very rapidly to a mini- 

 mum of 9.5° to 9.8° at about 49° west longitude. Further west- 

 ward the temperature increases again to a maximum of 13.6° 

 to 13.9° C. between 57° and 59° west longitude, and from there 

 on towards the American coast it diminishes to a new value of 

 about 5° C. The great falling off at 49° west longitude marks 

 with great distinctness the above mentioned cold " wedge ". When 

 one studies the temperature distribution in the single years, he 

 finds that this " wedge " stays almost exactly in the same spot 

 throughout. From both curves, (fig. 10) for the surface tempera- 

 tures, we see that only a slight difference exists between the two 

 decade groups. In the eastern part of the region the difference is 

 particularly small. In the central part, it is on the whole in the 

 last decade (March- April) somewhat colder than in the first (Feb- 



