Surface‐Atmosphere Decoupling Prolongs Cloud Lifetime Under Warm Advection Due To Reduced Entrainment Drying
Surface‐Atmosphere Decoupling Prolongs Cloud Lifetime Under Warm Advection Due To Reduced Entrainment Drying
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DOI：
10.1029/2022gl101663
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发表时间：
2023-05
影响因子：
5.2
通讯作者：
Haipeng Zhang;Youtong Zheng;Seoung-Soo Lee;Zhanqing Li
中科院分区：
文献类型：
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作者：
Haipeng Zhang;Youtong Zheng;Seoung-Soo Lee;Zhanqing Li
在暖平流条件下，最初混合良好的层积云甲板可以保持阴天数十小时，尽管由于地面-大气去耦合(地面-大气界面的稳定)，海洋的水分供应被切断。在这项研究中，一组理想化的大涡模拟被用来研究暖空气平流如何影响预先存在的层积云甲板演变的物理机制。为了模拟暖空气平流，我们在双周期域内随时间线性降低海洋表面温度。在初始条件相同的情况下，层积云甲板在经历暖空气平流时比经历冷空气平流时更持久。这种持久性是由于脱钩导致的云顶夹带干燥减少所致，这一过程比脱钩导致的水分供应中断更有影响。当自由对流层变得更潮湿时，这种机制更加明显。讨论了这一机制与以前在暖平流条件下观测到的低层云量减少的相关性。
An initially well‐mixed stratocumulus deck can remain overcast for several tens of hours under warm‐advection conditions, although moisture supply is cut off from the ocean due to surface‐atmosphere decoupling (stabilization of the surface‐atmosphere interface). In this study, a set of idealized large‐eddy simulations were performed to investigate the physical mechanism of how warm‐air advection impacts the evolution of a pre‐existing stratocumulus deck. To mimic warm‐air advection, we decrease the sea surface temperature linearly over time in a doubly periodic domain. Given the same initial conditions, the stratocumulus deck is more persistent when experiencing warm‐air advection than cold‐air advection. This persistence is caused by reduced cloud‐top entrainment drying due to decoupling, a process more influential than the decoupling‐induced cutoff of moisture supply. This mechanism is more notable when the free troposphere becomes more humid. The relevance of the mechanism to previous observations of less low‐level cloudiness under warm‐advection conditions is discussed.