Laserfiche WebLink
<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />- 130 - <br /> <br />photograph. The fact that the branch is fairly broad at its tip indicates that <br /> <br /> <br />it entered a region of lower saturation than during the initial stage of its <br /> <br /> <br />growth. The isolated branch shown in Fig. 4.4 (b) has secondary growth on one <br /> <br /> <br />side only, probably as a result of the mode of fall after becoming detached <br /> <br /> <br />from its parent crystal. Also of interest are the two larg~ dendritic <br /> <br /> <br />extensions adjacent to: each other near one end of the branch and the third <br /> <br />. extension at the opposite end. This fragment was collected at -l20.c. <br /> <br /> <br />Fig. 4.4 (c) shows a stellar crystal with one branch severely stunted. It <br /> <br /> <br />seems likely that the original branch at this point broke off in the air and <br /> <br /> <br />some further ~owthfrom the vapor phase then took place at this point to <br /> <br /> <br />produce the stunted branch. Isolated branches of the type shown in Fig. 4.4 (a) <br /> <br /> <br />and 4.4 (b) were the most readily identifiable fragments of symmetrical ice <br /> <br /> <br />crystals. Portions of other crystals (e.g. columns. ,and needles) were more <br /> <br />difficult to identify but they were observed. Fig. 4.4 (d) shows a needle <br /> <br /> <br />both ends of which have undergone fragmentation. The needle is rimed along <br /> <br /> <br />one side. <br /> <br />It might be argued that the crystals described above. could have fragmented <br /> <br /> <br />whilst being collected rather than in the free air. We do not think that this <br /> <br /> <br />was the case for the following reasons. Fragmentation of ice crystals due to <br /> <br /> <br />impact on the "Formvar" coated film was generally quite obvious because the <br /> <br /> <br />fragments were clumped together on the film. The fragments referred to above, <br /> <br /> <br />on the other hand, were isolated on the film without any evidence of nearby <br /> <br /> <br />related fragments. Fragmentation due t~'collision with .the entrance slit of <br /> <br /> <br />the cloud partiGle sampler, or within the decelerator, is. also unlikely since <br /> <br /> <br />the isolated branches often showed considerable asymmetrical secondary growth <br /> <br />