Laserfiche WebLink
<br />. <br /> <br />6 <br /> <br />. <br /> <br />to 2.5 minutes, improved the model's empirical basis. However, the same <br /> <br /> <br />fundamental problems that plagued the calculations of Jayaweera continued <br /> <br />in the model of Miller and Young despite the increased sophistication and <br /> <br /> <br />use of better data. <br /> <br /> <br />Uncertainty existed not only in the application of experimental data but <br /> <br /> <br />in the factors affecting crystal growth. Both models used theoretically derived <br /> <br /> <br />results that had not been properly tested with experimental data for growth <br /> <br /> <br />periods lasting longer than a few minutes. Indeed, Fukuta (1969) has used <br /> <br /> <br />data obtained from his mixing chamber to compare with values obtained <br /> <br /> <br />from the Maxwellian growth equation modified to account for shape, <br /> <br /> <br />ventilation and nearby cloud droplets. His results showed that the equation <br /> <br /> <br />with the corrective factors was not sufficient to account for the behavior of <br /> <br /> <br />the growth process. Fukuta and Walter (1970) have shown that this was due <br /> <br />to a diffusion-kinetic factor. <br /> <br /> <br />Another effect not even considered in the works of both Jayaweera (1971) <br /> <br /> <br />and Miller and Young (1979) is accretion, which increases ice crystal size by <br /> <br /> <br />collecting water droplets and then freezing them onto the crystal surface. <br /> <br /> <br />Accretion has been theoretically studied in detail, but no experiment before <br /> <br /> <br />1980 was able to show under what conditions this mode becomes important. <br /> <br /> <br />Since some rain drops begin coalescence well within 10 minutes after <br /> <br /> <br />nucleation (Rogers,1979), accretion could possibly become important within <br /> <br /> <br />the same period. However, this conjecture could not be supported by <br /> <br /> <br />experiment. Thus, without experimental clarification data critical questions <br /> <br /> <br />about accretion remained unanswered. <br /> <br /> <br />In summary, then, the importance of obtaining accurate experimental <br /> <br />data of ice crystal growth for an indefinate period of time cannot be <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br />