| This study utilized the UCLA cloud physics wind tunnel and the IBM 3033 computer. The wind tunnel experiments were conducted using two separate procedures, depending on the size of the spherical particle. Particles less than 1 mm diameter, were melted in free fall while experiencing a time varying environmental temperature, similar to the variation of temperature it would encounter while freely falling in the atmosphere. Particles larger than 1 mm diameter have a tendency to wander towards the tunnel walls, requiring restraint by a thin nylon fiber frozen halfway through the particle. Using this fiber, the particle was suspended from above. Although attached to a thread, the particle's terminal velocity was constantly maintained during melting by keeping the fiber slack.; Particles less than 1 mm diameter usually undergo "sailing" motions upon melting due to the melting of surface protuberances. Once the protuberances are melted, the particle falls with no horizontal drift. The melting ice core was observed to remain tangent with the downstream end of the particle, resulting in an eccentric melting location. The meltwater itself was also observed to circulate due to the external shear of the air on the meltwater surface. For these small particles, no meltwater was shed.; Particles larger than 9 mm diameter were found to shed meltwater, with the fraction shed increasing with particle size. Particles between 9 mm and 5 mm diameter did not shed their meltwater, and did not develop an internal circulation. Particles between 1 mm and 5 mm, however, did develop a significant internal circulation, resulting in a conically shaped ice core.; For each of the above size ranges, melting theories are developed which are able to quantitatively describe the melting rates of these particles. |
