The structure and evolution of lower stratospheric frontal zones. Part 1: Examples in northwesterly and southwesterly flow
The structure and evolution of lower stratospheric frontal zones. Part 1: Examples in northwesterly and southwesterly flow
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平流层低层锋区的结构和演化。
DOI：
10.1002/qj.843
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发表时间：
2012
影响因子：
8.9
通讯作者：
Jonathan E. Martin
中科院分区：
文献类型：
--
作者：
Andrea A. Lang;Jonathan E. Martin
从基本状态变量的角度研究了平流层下部两个锋区的结构、演变和动力学。案例研究强调了高层急流锋（ULJF）系统的平流层下部和对流层上部锋部分的异步演变，以及西南气流和西北气流中平流层下部锋发展的一些实质性差异。在西北气流中，ULJF的演变特征是平流层下部锋沿着减弱，而对流层上部锋则减弱。在整个演变过程中，气旋性切变中的地转冷空气平流是平流层下部锋的主要特征。这种情况支持了对流层上层寒冷的局部急流核心下沉，通过倾斜削弱了平流层下层锋。这种下沉向下延伸的射流核心，它建议发挥了作用，在早期阶段的对流层锋生。在西南气流的情况下，ULJF的演变的特点是加强平流层下部锋和减弱对流层上部锋。一个垂直向上运动的深柱是由于对流层下部上升与对流沿着一个表面冷锋和对流层上部-平流层下部（UTLS）上升通过急流核心的叠加造成的，与平流层下部锋面大部分沿着气旋性切变中的地转暖空气平流相一致。UTLS上升位于平流层下部斜压性的冷边缘，通过倾斜加强了平流层下部锋区。这些低平流层锋面过程的对流层顶和下游的敏感天气的地形的影响进行了讨论。皇家气象学会
The structure, evolution and dynamics of two lower stratospheric frontal zones are examined from a basic state variables perspective. The case studies highlight the asynchronous evolution of the lower stratospheric and upper tropospheric frontal portions of upper level jet‐front (ULJF) systems, as well as some substantial differences in lower stratospheric frontal development that occur in southwesterly and northwesterly flow. The evolution of the ULJF in northwesterly flow was characterized by an initially intense but weakening lower stratospheric front along with an initially weak but intensifying upper tropospheric front. Throughout the evolution, geostrophic cold air advection in cyclonic shear characterized a substantial portion of the lower stratospheric front. This circumstance supported subsidence through the local jet core within the cold upper troposphere, weakening the lower stratospheric front via tilting. This subsidence extended downward below the jet core where it is suggested to have played a role in the early stages of upper tropospheric frontogenesis. In the southwesterly flow case, the evolution of the ULJF was characterized by a strengthening lower stratospheric front and a weakening upper tropospheric front. A deep column of upward vertical motion resulted from the superposition of lower tropospheric ascent associated with convection along a surface cold front and upper tropospheric‐lower stratospheric (UTLS) ascent through the jet core coincident with geostrophic warm air advection in cyclonic shear along large sections of the lower stratospheric front. The UTLS ascent, located on the cold edge of the lower stratospheric baroclinicity, served to intensify the lower stratospheric frontal zone via tilting. The implications of these lower stratospheric frontal processes on the topography of the tropopause and downstream sensible weather are discussed. Copyright © 2012 Royal Meteorological Society