The Dependence of Storm Longevity on the Pattern of Deep Convection Initiation in a Low-Shear Environment
The Dependence of Storm Longevity on the Pattern of Deep Convection Initiation in a Low-Shear Environment
复制标题
风暴寿命对低切变环境中深对流起始模式的依赖性
DOI：
10.1175/mwr-d-10-05036.1
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发表时间：
2011
影响因子：
3.2
通讯作者：
R. Wilhelmson
中科院分区：
文献类型：
--
作者：
A. Houston;R. Wilhelmson
利用低切变初始环境下进行的理想化云分辨模拟，研究了风暴寿命对深对流启动模式的敏感性(例如，多个准线性排列的初始深对流单体与一个孤立的深对流单体)。当使用一条热力线或浅层气团边界将多个深对流单体初始化为彼此接近时，就会产生长期风暴。然而，当孤立的深对流被启动时，所产生的风暴在启动后稳步衰减。这些结果表明，与引发孤立深对流的机制相比，在近距离引发多个深对流单体的拟线性机制，如预先存在的气团边界，可以导致更长时间的风暴。所进行的实验之间的本质区别是，孤立的初始风暴产生的冷池比使用准线性启动时要浅。有人认为，即使在垂直切变值较小的环境中，深层冷池也促进了深层强迫上升、系统的对流单体再发展，从而促进了长时间的风暴。两次模拟之间冷池深度的差异归因于冷空气到阵风锋面的水平通量的差异。对于单一的初始风暴，随后形成的少数对流单体仅提供有限的冷空气来源，导致冷池较浅，无法促进持续的上升气流重建。
The sensitivity of storm longevity to the pattern of deep convection initiation (e.g., multiple, quasi-linearly arranged initial deep convective cells versus an isolated deep convective cell) is examined using idealized cloud-resolving simulations conducted with a low-shear initial environment. When multiple deep convective cells are initialized in close proximity to one another using either a line of thermals or a shallow airmass boundary, long-lived storms are produced. However, when isolated deep convection is initiated, the resultant storm steadily decays following initiation. These results illustrate that a quasi-linear mechanism, such as a preexisting airmass boundary, that initiates multiple deep convective cells in close proximity can lead to longer-lived storms than a mechanism that initiates isolated deep convection. The essential difference between the experiments conducted is that an isolated initial storm produces a shallower cold pool than when a quasi-linear initiation is used. It is argued that the deep cold pools promote deep forced ascent, systematic convective cell redevelopment, and thus long-lived storms, even in environments with small values of vertical shear. The difference in cold pool depth between the simulations is attributed to differences in the horizontal flux of cold air to the gust front. With a single initial storm, the few convective cells that subsequently form provide only a limited source of cold air, leading to a cold pool that is shallow and incapable of fostering continued updraft redevelopment.