Laboratory Studies -31- 



Another activity concerned itself with devising means of sampling 

 raindrops and measuring diameter. (3) 



Seeding with water drops was carried out with apparent success in 

 tropical clouds .^-U This is more fully discussed in a later section of 

 this report. ? (J?age 43) 



CONDENSATION NUCLEI 



Condensation nuclei played an important role in the behavior of the 

 atmosphere. In 1948 Vonnegut devised a method of obtaining a continuous 

 record of the concentration of condensation nuclei in the atmosphere.^" '' 

 Various experiments were conducted with this equipment, both aground 

 and aloft. The results suggest that the continuous measurement of the con- 

 centration of condensation nuclei may be very useful in meteorological in- 

 vestigations. 



ELECTRICAL PHENOMENA 



It was observed in 1943 by Schaefer that interesting atmospheric 

 electrical measurements could be obtained by connecting one end of a 

 shielded cable to an insulated needle presented to the sky and the other 

 end to a sensitive recording microammeter, one side of which was well 

 grounded.^ ' Among the interesting observations made during successive 

 years was one to the effect that the data obtained with this instrument in- 

 dicated the passage of charged clouds over the observation point. 



Continuous records were kept by Falconer from 1948 on, using the 

 data provided by this equipment, and an attempt was made to correlate 

 the measured corona -discharge currents with other meteorological phe- 

 nomena, such as frontal passages, wind direction, precipitation, and re- 

 flected light from the northern sky. It was found that there was generally 

 good agreement between such findings and those of other investigators. 



Best correlations obtained with this equipment seemed to be with 

 frontal passages associated with the arrival of new air masses and the 

 occurrence of precipitation not necessarily local but possibly extending 

 to a radius of a few hundred miles. But correlation was also obtained 

 with wind shifts and pressure changes, since frontal passages were 

 associated with those phenomena. There also seemed to be some re- ' 



lation between certain instrument indications and small, sharp changes 

 in the reflected light from the northern sky, particularly in apparently 

 clear skies. ^ ' 



