부산대학교 도서관

We generated a large number 105,000 of aggregates composed of various monomer types and sizes using an aggregation model. Combined with hydrodynamic theory, we derived ice particle properties such as mass, projected area, and terminal velocity as a function of monomer number and size. This particle ensemble allows us to study the relation of particle properties with a high level of detail which is often not provided by in situ measurements. The ice particle properties change rather smoothly with monomer number. We find very little differences in all particle properties between monomers and aggregates at sizes below 1 mm which is in contrast to many microphysics schemes. The impact of the monomer type on the particle properties decreases with increasing monomer number. Whether, for example, the terminal velocity of an aggregate is larger or smaller than an equal‐size monomer depends mostly on the monomer type. We fitted commonly used power laws as well as Atlas‐type relations, which represent the saturation of the terminal velocity at large sizes (terminal velocity asymptotically approaching a limiting value) to the data set and tested the impact of incorporating different levels of complexity with idealized simulations using a 1D Lagrangian super particle model. These simulations indicate that it is sufficient to represent the monomer number dependency of ice particle properties with only two categories (monomers and aggregates). The incorporation of the saturation velocity at larger sizes is found to be important to avoid an overestimation of self‐aggregation of larger snowflakes. Plain Language Summary: We have simulated and analyzed the properties, such as mass, area, and terminal fall velocity of snowflakes using a computer model. The snowflakes in the atmosphere form by collisions of ice crystals present in many different shapes. In the computer model, ice crystal shapes typically found in the atmosphere are stuck together to create three‐dimensional snowflakes. The properties of the snowflakes depend on the shape and the number of ice crystals that are stuck together. While in weather and climate models, the properties of ice crystals and snowflakes are often assumed to be very different even if they are of the same size, we find very little differences in their properties. Many weather and climate models assume that snowflakes have a higher fall velocity the larger they are, although field observations have shown that particles larger than a few millimeters all fall with similar velocity. We fitted new parameterizations of the particle velocities which can remove this deficiency in the models. Finally, we used another model and showed that it might be sufficient to divide the properties of the ice particles in only two categories. However, it is important to consider the almost constant velocity of the large snowflakes. Key Points: We simulated aggregates to study the impact of monomer number and type onice particle propertiesIce particle properties show a smooth transition from monomers to aggregatesThe saturation of terminal velocity needs to be taken into account when simulating snow aggregation [ABSTRACT FROM AUTHOR]