论文标题
在理想化的一般循环模型中，非洲东方波浪：不稳定性和波袋诊断
African Easterly Waves in an Idealized General Circulation Model: Instability and Wavepacket Diagnostics
论文作者
论文摘要
我们使用理想化的一般循环模型研究了在现实的，空间非均匀的非均匀的非均质东方喷气（AEJ）中产生的非洲东方波浪（AEW）的群体动态。我们的目标是研究AEJ的有限层面范围是否是AEW发展的障碍。我们使用全球重新分析场构建了一系列基本状态，并通过在西非的瞬时加热来初始化波浪。主要响应是一个局部的波袋，它分散了上游和下游。在大多数情况下，包含边界层的粗表示会稳定波。但是，在某些基本状态下，即使在阻尼的情况下，指数增长也会发生。这表明AEWS偶尔会自发出现。关键结果是波袋在几乎所有情况下都保留在AEJ内，而不是被扫除。从其他研究中汲取灵感，这也表明，如果与其他能量来源（例如潮湿对流和灰尘辐射反馈）相结合，即使是阻尼的波浪也可以增长。局部AEJ中的波袋似乎满足了绝对不稳定性的条件，即一种空间流体动力不稳定性的形式。但是，这需要更严格地进行验证。我们的结果还表明，AEWS的间歇性是介导的，不是通过对流和绝对不稳定性之间的过渡，而是通过诸如传播赤道波模式之类的外部来源的过渡。
We examine the group dynamic of African easterly waves (AEW) generated in a realistic, spatially non-homogeneous African easterly jet (AEJ) using an idealized general circulation model. Our objective is to investigate whether the limited zonal extent of the AEJ is an impediment to AEW development. We construct a series of basic states using global reanalysis fields and initialize waves via transient heating over West Africa. The dominant response is a localized wavepacket that disperses upstream and downstream. The inclusion of a crude representation of boundary layer damping stabilizes the waves in most cases. In some basic states, however, exponential growth occurs even in the presence of damping. This shows that AEWs can occasionally emerge spontaneously. The key result is that the wavepacket in almost all cases remains within the AEJ instead of being swept away. Drawing from other studies, this also suggests that even the damped waves can grow if coupled with additional sources of energy such as moist convection and dust radiative feedback. The wavepacket in the localized AEJ appears to satisfy a condition for absolute instability, a form of spatial hydrodynamic instability. However, this needs to be verified more rigorously. Our results also suggest that the intermittent nature of AEWs is mediated, not by transitions between convective and absolute instability, but likely by external sources such as propagating equatorial wave modes
