Abstract. We explore the impacts of the diurnal cycle, free-tropospheric (FT) humidity values, and interactive surface fluxes on the cloud system evolution of non-precipitating marine stratocumuli based on a large ensemble of large-eddy simulations. Cases are separated into three categories based on their degree of decoupling and cloud liquid water path (LWP_c). A new budget analysis method is proposed to analyze the evolution of LWP_c under both coupled and decoupled conditions. More coupled clouds start with relatively low LWP_c and cloud fraction (f_c) but experience the least decrease in LWP_c and f_c during the daytime. More decoupled clouds undergo greater daytime reduction in LWP_c and f_c, especially those with higher LWP_c at sunrise because they suffer from faster weakening of a net radiative cooling. During the nighttime, a positive correlation between FT humidity and LWP_c emerges, consistent with higher FT humidity reducing both radiative cooling and the humidity jump, both of which reduce entrainment and increase LWP_c. The time rate of change in the LWP_c is more likely to be negative for higher LWP_c and greater inversion base height (z_i), conditions under which entrainment dominates as turbulence develops. In the morning, the rate of the LWP_c reduction depends on the LWP_c at sunrise, z_i, and the degree of decoupling, with distinct contributions from subsidence and radiation. Under well-mixed conditions, it takes about 10 h for the surface fluxes to offset 15 % of the changes in entrainment warming and drying, assuming no changes in transfer coefficients or surface wind speed.

中文翻译：

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LES 系综中非降水海洋层积的日演化

摘要。我们基于大涡模拟的大型集合，探讨了昼夜循环、自由对流层 (FT) 湿度值和交互表面通量对非降水海洋层积云云系统演化的影响。根据解耦程度和云液态水路径（LWP _c），案例分为三类。提出了一种新的预算分析方法来分析耦合和解耦条件下LWP _c的演化。更多耦合的云开始时具有相对较低的 LWP _c和云分数 ( f _c )，但在白天LWP _c和f _c的下降幅度最小。更多的解耦云在白天的 LWP _c和f _c会经历更大的减少，特别是那些在日出时 LWP _c较高的云，因为它们的净辐射冷却减弱得更快。在夜间，FT 湿度和 LWP _c之间出现正相关，这与较高的 FT 湿度减少辐射冷却和湿度跳跃一致，这两者都减少夹带并增加 LWP _c。对于较高的 LWP _c和较大的逆温底高度 ( z _{i )，LWP c}的时间变化率更有可能为负，在这种情况下，随着湍流的发展，夹带占主导地位。早上，LWP _c减少的速率取决于日出时的LWP _c z _i和解耦程度，其中沉降和辐射的贡献明显。在充分混合的条件下，假设传递系数或表面风速没有变化，表面通量大约需要 10 小时才能抵消夹带升温和干燥变化的 15%。