Climate models rely on parameterizations of a variety of processes in the atmospheric physics, but a common concern is that the temporal resolution is too coarse to consistently resolve the behavior that individual parameterizations are designed to capture. This study examines timescales numerically derived from the Morrison‐Gettelman (MG2) microphysics as implemented within the Energy Exascale Earth System Model, version 1 (E3SMv1). Numerically relevant timescales in MG2 are derived by computing the eigenspectrum of its Jacobian. These timescales are found to often be smaller than the default 5 min time step used for MG2. The fast timescales are then heuristically connected to individual microphysics processes. By substepping a few particular rain processes within MG2, the time discretization error for those processes was considerably reduced with minimal additional expense to the overall microphysics. While this improvement has a substantial effect on the target processes and on the vertical distribution of stratiform‐derived rain within E3SMv1, the overall model climate is found to not be sensitive to MG2 time step. We hypothesize that this is because the surface climate does not depend strongly on certain process rates, especially MG2's rain evaporation rate.

中文翻译：

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MG2微观物理模型中与数字相关的时标

气候模型依赖于大气物理学中各种过程的参数化，但是一个共同的问题是时间分辨率太粗糙而无法一致地解决单个参数化旨在捕获的行为。这项研究研究了从莫里森-盖特曼（MG2）微观物理学数值推导的时间尺度，该尺度是在能源亿亿地球系统模型版本1（E3SMv1）中实现的。MG2中与数字相关的时标是通过计算其Jacobian的本征谱得出的。发现这些时间尺度通常小于用于MG2的默认5分钟时间步长。然后将快速的时标启发式地连接到单个微物理学过程。通过细分MG2中的一些特定降雨过程，这些过程的时间离散误差大大降低，而对整个微观物理学的额外花费却最小。尽管此改进对目标过程和E3SMv1中层状降雨的垂直分布有很大影响，但发现总体模型气候对MG2时间步阶不敏感。我们假设这是因为地表气候在很大程度上不取决于某些处理速率，尤其是MG2的雨水蒸发速率。