Cumulus Studies -50- 



_ "At 10:06, when the top of the cloud was 36,000 feet (temperature 

 -49°C), the first radar echo return was obtained from the cloud 

 at an altitude of 20,500 feet (temperature -9°C). The distance 

 given by radar was 25 miles at an azimuth of 165°, which was 

 exactly where the cloud was found to be from visual observations. 

 The area p precipitation in the cloud was about one square mile 

 at that time and was deep within the mass of the cloud. Within 

 four minutes, the precipitation area had increased to seven 

 square miles, and within six minutes after the first echo ap- 

 peared, the precipitation had extended upward to 34,000 feet, 

 where the temperature 'was -43°C„ 



"The chain reaction in this cloud started at low altitude at 

 a time and place which agreed well with the trajectory of the 

 silver -iodide smoke. 



"The first flash of lightning was seen at 10:10, four minutes 

 after the first radar echo was detected. In all, perhaps a dozen 

 flashes of lightning formed from this cloud, and very heavy rain 

 was seen to fall to the ground. The top of the cloud moved to- 

 wards the W, but the lower part of the cloud, from which the 

 rain was falling, moved gradually to the NE„ 



"At 10:45, a second cloud about eight miles still further 

 to the NE developed a radar echo, and from that time on during 

 the day there was an increasing number of rainstorms giving 

 very heavy showers in the neighborhood. During the late after- 

 noon 1.2 inches of rain fell at the station where the generator 

 was located. The phenomena observed near and at Albuquerque 

 from the ground and the radio reports of exceptionally heavy 

 rain at Santa Fe gave immediate evidence of the success of this 

 operation in producing heavy rain." 



Langmuir's report then analyzes river flow data and rain gauge data 

 for the region. In discussing the rain gauge data, he says: 



"The Weather Eureau observer with Project Cirrus in 

 New Mexico stated that he considered it possible or even prob- 

 able that seeding operations carried on there could have in- 

 creased the naturally occurring rain by five per cent, but certainly 

 not more than 10 per cent. If this were ture, it would be possible 

 to conclude that seeding operations have economic value only if 

 experiments are carried on many hundred of days, and a statis- 

 tical analysis is made of the rainfall data for all of these oper- 

 ations. 



