The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics
The life cycle of upper-level troughs and ridges: a novel detection method, climatologies and Lagrangian characteristics
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高层海槽和山脊的生命周期：一种新颖的检测方法、气候学和拉格朗日特征
DOI：
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发表时间：
2020
影响因子：
--
通讯作者：
M. Sprenger
中科院分区：
文献类型：
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作者：
S. Schemm;Stefan Rüdisühli;M. Sprenger
抽象的。引入了一种新方法来识别和跟踪上层海槽和山脊的生命周期。其目的是缩小检测上层罗斯贝波发展起始阶段的方法与检测罗斯贝波破碎波和衰减波的方法之间存在的差距。该方法量化了水平槽和脊方向并识别相应的槽和脊轴。这些使我们能够分别研究海槽-山脊之前和之后区域的动态。该方法基于给定等压面处的位势高度的曲率，并且计算效率高。时空跟踪使我们能够量化槽和脊的成熟度，也可用于研究槽或脊方向的时间演化。首先，详细介绍该算法，并讨论了几个示例性应用（例如从北大西洋到地中海的下游开发）和季节性气候。例如，气候槽和脊的方向显示出强烈的纬向和经向不对称性：在陆地上，大多数槽和脊是反气旋方向的，而在主要海洋风暴路径上它们是气旋方向的；气旋方向朝两极增加，而反气旋方向朝赤道增加。从气候学角度来看，落基山脉下游以及东亚和东欧的低谷检测频率较高，但格陵兰岛下游的低谷检测频率却非常低。此外，在北太平洋风暴路径末端和不列颠群岛上空的北大西洋风暴路径末端，低压槽的检测频率较高。在受厄尔尼诺影响的冬季，北美和北大西洋的海槽和海脊表现出异常强烈的气旋倾斜，这与之前基于传统方差诊断（例如 E 矢量）的发现一致。在拉尼娜现象期间，情况基本相反。槽和脊的方向也取决于喷射位置。例如，在太平洋的仲冬期间，副热带急流最强且位于赤道最远的时候，气旋性的槽和脊主导了气候。最后，将识别的槽和脊用作 24 小时向后地块轨迹的起点，并讨论沿轨迹的压力、位温和位涡变化的分布，以深入了解槽和脊的三维性质。
Abstract. A novel method is introduced to identify and track the life cycle of upper-level troughs and ridges. The aim is to close the existing gap between methods that detect the initiation phase of upper-level Rossby wave development and methods that detect Rossby wave breaking and decaying waves. The presented method quantifies the horizontal trough and ridge orientation and identifies the corresponding trough and ridge axes. These allow us to study the dynamics of pre- and post-trough–ridge regions separately. The method is based on the curvature of the geopotential height at a given isobaric surface and is computationally efficient. Spatiotemporal tracking allows us to quantify the maturity of troughs and ridges and could also be used to study the temporal evolution of the trough or ridge orientation. First, the algorithm is introduced in detail, and several illustrative applications – such as a downstream development from the North Atlantic into the Mediterranean – and seasonal climatologies are discussed. For example, the climatological trough and ridge orientations reveal strong zonal and meridional asymmetry: over land, most troughs and ridges are anticyclonically oriented, while they are cyclonically oriented over the main oceanic storm tracks; the cyclonic orientation increases toward the poles, while the anticyclonic orientation increases toward the Equator. Trough detection frequencies are climatologically high downstream of the Rocky Mountains and over East Asia and eastern Europe but are remarkably low downstream of Greenland. Furthermore, the detection frequencies of troughs are high at the end of the North Pacific storm track and at the end of the North Atlantic storm track over the British Isles. During El Niño-affected winters, troughs and ridges exhibit an anomalously strong cyclonic tilt over North America and the North Atlantic, in agreement with previous findings based on traditional variance-based diagnostics such as E vectors. During La Niña, the situation is essentially reversed. The orientation of troughs and ridges also depends on the jet position. For example, during midwinter over the Pacific, when the subtropical jet is strongest and located farthest equatorward, cyclonically oriented troughs and ridges dominate the climatology. Finally, the identified troughs and ridges are used as starting points for 24 h backward parcel trajectories, and a discussion of the distribution of pressure, potential temperature and potential vorticity changes along the trajectories is provided to give insight into the three-dimensional nature of troughs and ridges.
影响因子：
8.9
作者：
C. Grams;H. Wernli;M. Böttcher;J. Čampa;U. Corsmeier;S. Jones;J. Keller;C. Lenz;L. Wiegand-
通讯作者：
C. Grams;H. Wernli;M. Böttcher;J. Čampa;U. Corsmeier;S. Jones;J. Keller;C. Lenz;L. Wiegand-