Arctic mixed‐phase clouds simulated by the U.S. Department of Energy (DOE) Energy Exascale Earth System Model (E3SM) Atmosphere Model version 1 (EAMv1) are found to be overly dominated by supercooled liquid with little ice production. Sensitivity experiments using the short‐term hindcast approach are performed to isolate the impact of several new parameterizations on the simulated mixed‐phase clouds in EAMv1. These include the Classical Nucleation Theory (CNT) ice nucleation scheme, the Cloud Layer Unified By Binormals (CLUBB) parameterization, and the updated Morrison and Gettelman microphysics scheme (MG2). Results are compared to the DOE's Atmospheric Radiation Measurement (ARM) Mixed‐Phase Arctic Cloud Experiment (M‐PACE) observations. It is found that all of these new parameterizations are responsible for the decrease of cloud ice water content in EAMv1 simulated single‐layer mixed‐phase clouds. A budget analysis of detailed cloud microphysical processes suggests that a lack of initial ice particles from ice nucleation or convective detrainment strongly diminishes the cloud ice water content through the subsequent ice mass growth processes. Reduced heterogeneous ice nucleation by CNT at temperatures warmer than −15°C along with negligible ice processes in CLUBB are primarily responsible for the problem. Because the use of MG2 does not impact initial ice formation, the MG2 cloud microphysics is not the primary reason for the underestimate of cloud ice. However, using MG2 leads to a lower total ice mass due to a higher accretion rate of liquid droplets by rain drops and a lower ice mass growth rate.

中文翻译：

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理解E3SM中北极单层混合相云的模拟相分区

由美国能源部（DOE）的能量百亿亿地球系统模型（E3SM）大气模型版本1（EAMv1）模拟的北极混合相云被过冷的液体过分控制，几乎没有产冰。进行了使用短期后验方法的敏感性实验，以隔离几个新参数化对EAMv1中模拟混合相云的影响。其中包括经典成核理论（CNT）冰成核方案，双法线统一云层（CLUBB）参数化以及更新的Morrison和Gettelman微物理学方案（MG2）。将结果与美国能源部的大气辐射测量（ARM）混合相北极云实验（M-PACE）观察结果进行比较。发现所有这些新的参数化都是导致EAMv1模拟的单层混合相云中云冰水含量减少的原因。对详细的云微物理过程进行的预算分析表明，由于冰成核或对流脱轨而缺乏初始冰粒，从而在随后的冰块生长过程中大大降低了云冰中的水含量。碳纳米管在低于-15°C的温度下减少的异质冰成核作用以及CLUBB中可忽略的制冰过程是造成该问题的主要原因。由于MG2的使用不会影响初始冰的形成，因此MG2云的微观物理学并不是低估云冰的主要原因。然而，