NO. 4 TEMPERATURE VARIATIONS IN THE NORTH ATLANTIC III 



great is the similarity if we omit from the calculation of the mean 

 value- the most easterly and most westerly io° fields, and confine 

 ourselves to the middle part as we have done in figure 49 (see also 

 fig-. 51 and 52). We see that in these curves the agreement with 

 few exceptions might be called complete. 



The values found for the single fields in the Portugal-Azores 

 region in many cases show poorer agreement (compare pis. 44 and 

 45). But it must be remembered on the o'ne hand, that our obser- 

 vational material here is less complete, that is, on the whole there 

 are fewer observations for these fields. On the other hand, our 

 process of determining the strength and direction of the wind is 

 not accurate enough for this region, where we are in the influence 

 of the anti-cyclonic high-pressure region near the Azores and also 

 approach the region of the trades. However, the average of the 

 fields, as shown in figures 50 to 52, has remarkably good agreement, 

 in fact even a more complete agreement than in most of the other 

 regions. 



In the 10° longitude fields of the Danish observations north of 

 50" north latitude, as we have already said, we have based the values 

 found for the surface temperatures on too few observations, so 

 that we could not expect here as completely satisfactory agreement 

 as elsewhere. In this region of the ocean, furthermore, the air 

 pressure observations for the months within which our investiga- 

 tion is confined are so few in number and are so scattered that 

 the monthly isobars on the charts are somewhat hypothetical. How- 

 ever, in spite of this we have drawn curves of the air pressure 

 gradients and the surface temperatures both for January-Febru- 

 ary and for March- April for these 10° longitude fields (see pi. 46). 

 We find the agreement between them better than the unsatisfactory 

 quality of the material would lead us to expect, particularly for 

 the field between 30° and 39° west longitude. In the most easterly 

 field here, as also farther south, the agreement between the curves 

 for the air pressure gradients and for the surface temperatures is 

 not very good. But these curves have a similarity with the cor- 

 responding more southerly ones. 



If the wind is a principal cause of most of the observed varia- 

 tions in the surface temperature from year to year, then we must 

 expect that variations in the direction of the isobars and the in- 

 tensity of the air pressure gradients would primarily influence the 

 air temperature and bring still greater variations in this than in 

 the surface temperature of the ocean. Our curves in figures 48 



