Entrainment‐mixing mechanisms significantly affect cloud droplet number concentration, radius, and spectral shape. Quantitative examination of entrainment‐mixing effects on cloud droplet spectral width is lacking. This study examines the effects of entrainment‐mixing processes on cloud microphysics by 12,218 different setups, each simulated 10 times using the Explicit Mixing Parcel Model (EMPM) driven by the observational data from the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX‐III) campaign. Parameterizations of entrainment‐mixing mechanisms are developed by relating homogeneous mixing degree to transition scale number that depends on the dissipation rate and droplet evaporation time scale. The correlation between relative dispersion of cloud droplet size distribution and homogeneous mixing degree changes from negative to positive with the decreasing homogeneous mixing degree. The different relationships are closely related to the competition between complete and partial droplet evaporation and the number concentration of small droplets, which are quantitatively described by two newly introduced dimensionless numbers. The competition is significantly affected by relative humidity and mixing fraction of entrained air as well as turbulence dissipation rate, but not much by cloud droplet number concentration. Especially, when relative humidity and dissipation rate are high, there is only a negative correlation. This study sheds new light on generalizing the homogeneous/inhomogeneous concept by considering relative dispersion and also provides parameterizations of entrainment‐mixing processes and relative dispersion for atmospheric models.

中文翻译：

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基于数值模拟的夹带机制参数化及其对云滴谱宽的影响

夹带混合机制显着影响云滴数浓度，半径和光谱形状。缺乏对夹带混合对云滴谱宽的影响的定量检查。这项研究通过12218种不同的设置，研究了夹带混合过程对云微物理学的影响，每种设置均使用由第三次青藏高原大气科学实验（TIPEX-III）活动的观测数据驱动的显式混合包裹模型（EMPM）进行了10次模拟。通过将均匀混合度与过渡尺度数相关联来开发夹带混合机制的参数化，过渡数取决于耗散率和液滴蒸发时间尺度。随着均匀混合度的降低，云滴尺寸分布的相对分散度与均匀混合度之间的相关性从负变为正。不同的关系与完全和部分液滴蒸发之间的竞争以及小液滴的数量浓度密切相关，这由两个新引入的无量纲数进行定量描述。竞争受到相对湿度和夹带空气的混合分数以及湍流耗散率的显着影响，但不受云滴数量浓度的影响很大。特别地，当相对湿度和耗散率高时，仅存在负相关。