This investigation presents simulated environments of ice crystals to computer analysis as a means of imitating particle measurements made by electro-optical devices such as the Particle Measuring System's 1-D instrument. A mathematical model is developed so that single crystals of known geometric form can be processed by considering each crystal's spatial relationship to the assumed measuring instrument. Crystal orientation is defined using a random number technique. The results of the assumed measurements are converted into mass of equivalent liquid water by different methods and are compared with the known mass of the simulated environment. Relationships are derived for the conversion of several forms of single ice crystals into terms of equivalent melted diameters of liquid water and a comparison is made between the mass calculated from the derived equations with the conversion equations relating measured length to equivalent melted diameter currently in use.

The microphysics of Large Scale Cloud Systems (LSCS) was investigated by in-situ measurements made from two specially instrumented aircraft, a United States Air Force MC-130E and a Learjet 36 Information was obtained on the distribution of liquid and ice water content, particle size distributions, crystal habits, and other meteorological variables. The morphologies of three storms were investigated in detail as the storms crossed the United States.

This report summarizes previous melting-layer research both within and outside AFGL and provides recommendations for future research in the melting layer. An extensive literature search provided a bibliography of previous research. This bibliography is included as an appendix. Several definitions of the top and bottom of the melting layer are presented and discussed. Aggregation and breakup appear to be the chief microphysical processes that determine the particle-size spectrum of snow and ice that enter the melting layer. Studies of the actual melting process and of the melting layer as seen by radar are presented. Microphysical and thermodynamic characteristics are discussed. Dynamic considerations are mentioned. Previously gathered aircraft data are reviewed, and recommendations are made for future aircraft and radar data-gathering efforts. (Author).

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