THE NUMBER OF CONDENSATION NUCLEI OVER THE ATLANTIC AND PACIFIC OCEANS 



During cruise VII of the Carnegie . 755 sets of ob- 

 servations were made with an Aitken nuclei counter. 

 Generally a single set was made each day except when a 

 diurnal-variation series was started. Occasionally sev- 

 eral sets were made on some particular day, usually to 

 test some point that was raised in the observer's mind 

 at the time. Of the diurnal-variation series attempted, 

 sixteen were completed or essentially completed during 

 the cruise. Excluding all sets of each diurnal-variation 

 series except the first and last, there was a total of 365 

 sets of nuclei observations. The values of nuclei content 

 in the .365 sets were distributed as shown in table 1 be- 

 low. It is thus seen that the majority of the measure- 

 ments fall into the lower nuclei content groups. On 144 

 occasions the nuclei were found to be less than 1000 per 

 cc, while on only 15 occasions did the nuclei rise above 

 10,000 per cc. Nearly three -fourths of all the observa- 

 tions listed in table 1 gave a nuclei content less than 

 2500 per cc. Thus it is seen that, contrary to what is so 



Table 1. Distribution of values of nuclei content 

 for cruise VH 



frequently found over land, the nuclei over the ocean 

 generally are few in number. The nuclei content varied 

 considerably from one leg to another of the cruise. This 

 fact is brought out in table 2 (1). 



The data in table 2 include all sets in the diurnal- 

 variation series as well as those taken once or only a 

 few times each day. In obtaining the means in the table, 

 six sets taken on July 8 and 9, 1928, at the mouth of the 

 Elbe River, were excluded from the Hamburg-Reykjavik 

 leg of the cruise. The mean of the six excluded sets is 

 8910. Had they been included with the other values, the 

 mean for this leg would have been increased to 3720 and 

 the average number of nuclei per cc for the five largest 

 values would have been increased to 10,570. 



That large values of nuclei were found at the mouth 

 of the Elbe emphasizes the possibility that an industrial 

 region on land can affect the ocean values of nuclei for a 

 considerable distance from shore. This point is still 

 further emphasized by observations taken on the Carne- 

 gie as the ship receded from the vicinity of Europe. A 

 map showing this leg of the cruise is given m figure 16. 

 The map gives the number of nuclei per cc measured at 

 various localities, with arrows indicating the direction 

 and force of the wind at each locality. A number 

 representing wind force on the conventional Beaufort 

 scale is inset in the circle attached at the end of each 

 arrow. It is seen that, as the ship left the vicinity of 

 Europe, the nuclei content of the air gradually diminished. 

 It is apparent that even at considerable distances from 

 land, during those occasions when the wind blew from the 

 direction of land on which there was considerable indus- 

 trial activity, the ocean values are unusually large. 



In the Pacific Ocean the nuclei content of the air in- 

 creased to considerable values shortly before the ship 



Table 2. Nuclei content of the air over the oceans from observations on the Carnegie between 



May 1928 to November 1929 



Ocean 



Leg of cruise 



Dates 



No. 



of 



sets 



Average nuclei per cc 



5 

 largest 

 values 



smallest 

 values 



All 

 values 



Means 



635 



6090 



960 



2350 



Means for whole cruise 755 



5320 



810 



2200 



153 



