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<br />. <br /> <br />3 <br /> <br />. <br /> <br />Ice crystals were gathered in airplanes by Ono (1969 and 1970), but <br /> <br /> <br />additional problems existed. The impact during the collection processes <br /> <br /> <br />tended to damage the ice particles, and the effects of the airspeed created <br /> <br /> <br />difficulties in fall velocity measurements. In order to resolve some of these <br /> <br /> <br />problems, Magono and Tazawa (1966) used balloons to collect the particles <br /> <br /> <br />and determined atmospheric conditions. Still, such information as the <br /> <br /> <br />particle's growth history was missing. <br /> <br /> <br />Laboratory experiments have the advantage over the field studies during <br /> <br /> <br />the entire growth period, but the investigators could not effectively simulate <br /> <br /> <br />the natural growth conditions. Using static methods, investigators such as <br /> <br /> <br />Hallett and Mason (1958), Hallett (1965) and Kobayashi (1%1) grew crystals on <br /> <br /> <br />thin fibers under controlled supersaturation. However, the free fall condition <br /> <br /> <br />of the naturally growing crystal was not simulated, and no terminal velocity <br /> <br /> <br />was measured. Fukuta (1969), Ryan, Wishart and Shaw (1976) and others <br /> <br /> <br />have studied ice crystal growth under free fall in the environment of <br /> <br /> <br />controlled conditions, but only the former simultaneously determined the <br /> <br /> <br />velocity, Unfortunately, until about 1980, no method could suspend the <br /> <br /> <br />growing crystal for more than 3 minutes. Since the growth time of free <br /> <br /> <br />falling ice crystals in the natural cloud is typically more than 30 minutes, a <br /> <br />large void in experimental data still existed. <br /> <br /> <br />This data void has presented the cloud physicist a number of problems. <br /> <br /> <br />One such problem was the inability to test theoretical results for longer than 3 <br /> <br /> <br />minutes. For example, a theoretical result, the Maxwellian equation for <br /> <br />vapor diffusional growth, expresses the mass of ice crystals with low fall <br /> <br /> <br />velocities, and, until recently, no data for crystals grown under controlled and <br /> <br /> <br />naturally simulated conditions were available to properly test the theory. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br />