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<br />. <br /> <br />11 <br /> <br />. <br /> <br />condensation freezing and by freezing existing droplets. The swinging action <br /> <br />dispersed the ice crystals, and kept the concentration to within 1 to 10 em.) to <br /> <br /> <br />prevent moisture exhaustion. However, the sizes of these particles varied <br /> <br /> <br />over some range and, thus, the nucleation method introduced uncertainty of <br /> <br /> <br />the starting time of growth. After nucleation, an opening at the bottom <br /> <br /> <br />allowed the crystals to faU into the lower chamber. <br /> <br /> <br />The lower chamber furnished the growth environment for the faIling <br /> <br /> <br />crystals. In the chamber, thermocouples monitored the temperature at two <br /> <br /> <br />locations, A strip chart recorder provided a hardcopy of the readings, which <br /> <br /> <br />never varied by more than 0.2'C. When the crystals fell to a point near the <br /> <br /> <br />bottom, a camera under the illumination with a chopped beam photographed <br /> <br /> <br />the particle's motion to determine the faU velocity. Just above this point a <br /> <br /> <br />metal screen suppressed any possible turbulence but aUowed steady ambient <br /> <br /> <br />downdrafts to develop from the particle's motion. When the crystal reached <br /> <br /> <br />the bottom, a glass slide coated with silicon oil caught and preserved the <br /> <br /> <br />particle, which could be rotated in any direction under the microscope, so that <br /> <br /> <br />the diameter and height could be determined. Applied hot air then melted <br /> <br /> <br />the crystal so that the radius of the resultant drop and, thus, the mass could be <br /> <br />obtained. <br /> <br /> <br />During the experimental study, ice crystals freely feU and grew in air <br /> <br /> <br />saturated with respect to liquid water at temperatures between -4 and -20De. <br /> <br /> <br />Quantities that were measured included ice crystal mass after approximately <br /> <br /> <br />27, 37 and 47 seconds; a- and c-axiallengths after 47 seconds, and faU velocity <br /> <br /> <br />after 20, 37, 47, 60 and 70 seconds of growth. The data set provides useful <br /> <br /> <br />information on ice crystal microphysics, yet technical limitations have <br /> <br />reduced the quality of the data set. As previously mentioned, the loading of <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br />