154 



OCEAN ATMOSPHERIC-ELECTRIC RESULTS 



reached Guam from Apia, and remained so throughout 

 most of the next leg of the cruise. It is of interest to 

 note that during this part of the cruise, the vessel was 

 in the vicinity of volcanos which might be expected to 

 contribute appreciably to the nuclei content of the at- 

 mosphere. It seems probable that the unusually high 

 nuclei content of the atmosphere found in this locality 

 was produced by the action of volcanos in the region. 



Of the sixteen complete or nearly complete diurnal- 

 variation series obtained during the cruise, none was 

 obtained in the Atlantic. The first series was made be- 

 tween Balboa and Easter Island, on November 13-14, 

 1928, and three additional series were obtained on the 

 same leg of the cruise. Three series were completed 

 between Callao and Papeete, and three between Apia and 

 Guam, one between Guam and Yokohama, two between 

 Yokohama and San Francisco, and three between Hono- 

 lulu and Pago Pago. It would seem desirable to deter- 

 mine if there is any systematic variation through the day 

 in the nuclei content of the atmosphere over the ocean, 

 when considered either on local or on universal time. 



In an effort to ascertain whether any systematic vari- 

 ation exists, the sixteen diurnal-variation series were 

 arbitrarily separated into four groups. Each day was 

 arranged according to local time and the hourly means 

 were obtained for each group. The four diurnal-varia- 

 tion curves are shown in figure 17A. It is easily seen 

 that the four groups are not systematic, that is, similar 

 in the type of variation they display. It is concluded, 

 therefore, that over the ocean the nuclei content of the 

 atmosphere does not vary systematically through the day 

 according to local time. In a similar manner, each day 

 in the various groups was arranged according to Green- 

 wich time and the hourly means were obtained for each 

 group. The four diurnal-variation curves thus obtained are 

 shown in figure 17B. It is seen that in this case, like- 

 wise, there is no systematic diurnal variation in the nu- 

 clei content of the atmosphere over the oceans according 

 to universal time. Any variation through the day that 

 has been observed, therefore, must have been of acci- 

 dental nature. 



Out of 755 sets of condensation nuclei shown in table 

 2, there were 225 sets which were made simultaneously 

 or nearly simultaneously with measurements of either 

 positive or negative small-ion content of the atmosphere. 

 These 225 setsof simultaneous data were grouped accord- 

 ing to the leg of the cruise, and the mean value for each 

 leg was obtained. For the Atlantic 44 sets were avail- 

 able, while for the Pacific there were 181 sets. A sum- 

 mary of the results is given in table 3. The mean values 

 for all 225 sets are 1776, 522, and 422 per cc, respec- 

 tively, for the nuclei, the positive ions, and the negative 

 ions. How "oj " was derived will be seen in what follows. 



The small ions of both signs should be more numer- 

 ous than indicated in table 3 if they are being destroyed 

 only through recombinations with each other. In this 

 case, assuming equilibrium conditions to exist, the num- 

 ber n of small ions of either sign per cc, positive and 

 negative ions being assumed equally numerous, can be 

 computed through the well-known equation. 



q = an'! 



(1) 



where q is the rate of production of ion pairs and a is 

 the recombination coefficient for small ions. The ioni- 

 zation over the oceans is due essentially to cosmic rays, 

 hence the mean value of q may be taken as about 1.4 ion 

 pairs per cc per second. A generally accepted value of 

 a is 1.6 X 10-6. Using these quantities, the value of n 

 is found to be 935. To account for the observed smaller 

 values of n, it is necessary to assume that the small 

 ions are being destroyed by some additional process be- 

 sides recombination. Condensation nuclei are known to 

 destroy the small ions by combining with them. When 

 combining occurs, the uncharged nucleus converts the 

 small ion into a large ion while the large ion neutralizes 

 the charge on the small ion. Assuming that the reduced 

 number of small ions in the air over the oceans is due to 

 the presence of condensation nuclei, it is possible to com- 

 pute the rate at which the nuclei combine with the small 

 ions and, further, on the basis of certain assumptions, to 

 compute the number of large ions per unit volume in the 



Table 3. Derived values of combination coefficient co based on simultaneous values of nuclei and 



small ions for all legs of cruise VII 



Ocean 



Leg 

 no. 



Leg of cruise 



Dates 



No. 



of 



sets 



Mean 

 per cc 



N, 



00 in 

 10-6 

 units 



Atlantic 



Pacific 



1 Newport News - Plymouth 



2 Plymouth - Hamburg 



3 Hamburg - Reykjav& 



4 Reykjavik - Barbados 



5 Barbados - Balboa 



6 Balboa - Easter Island 



7 Easter Island - Callao 



8 Callao - Papeete 



9 Papeete - Apia 



10 Apia - Guam 



11 Guam - Yokohama 



12 Yokohama - San Francisco 



13 San Francisco - Honolulu 



14 Honolulu - Pago Pago 



May 10 - June 8 

 June 18 - June 22 

 July 7 - July 20 

 July 27 - Sep. 16 

 Oct. 1 -Oct. 11 



Oct. 25 - Dec. 6 

 Dec. 12.- Jan. 14 

 Feb. 5 - Mar. 13 

 Mar. 20 - Apr. 1 

 Apr. 20 - May 20 

 May 25 - June 6 

 June 24 - July 28 

 Sep. 3 - Sep. 23 

 Oct. 2 - Nov. 18 



Total or means 225 



1776 



522 422 



