大西洋地区阻塞高压的子空间重构及动力过程的合成分析
投稿时间: 2017-06-01  最后修改时间: 2017-06-14  点此下载全文
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马继望 南京信息工程大学大气科学学院 nuistmajiwang@163.com 
中文摘要:本文应用梁湘三等人提出的局地多尺度能量涡度分析方法(MS-EVA)以及基于此方法导出的正则传输理论,从多尺度能量学的角度,分析了北大西洋地区阻塞高压生成、发展和消亡的机制。首先,应用多尺度子空间变换方法(MWT)将ERA-40资料的三维风场、温度场和位势高度场分解到三个尺度子空间:基本流尺度、阻塞高压尺度和天气尺度。在阻塞高压尺度中,主要的信号表现为一个西退的高压结构,并且在西退的过程中伴随着先增强后减弱的强度变化。在阻塞高压的演变中,其动能存在三个明显的阶段:强度较弱且相对稳定的生成阶段,迅速增强的发展阶段以及衰减的消亡阶段。进一步分析影响动能的各个因子,发现控制着三个阶段的机制明显不同:压力做功和来自天气尺度动能的正则传输使得阻塞高压生成;后者同时也是其快速发展的能量来源;而动能向有效位能的浮力转换过程则是导致阻高消亡的主要原因。
中文关键词:多尺度子空间变换,局地多尺度能量涡度分析,正则传输,阻塞高压,升尺度反馈
 
The multiscale window reconstruction and dynamical analysis of the Atlantic blockings
Abstract:Using the functional analysis machinery, multiscale window transform (MWT), and the MWT-based localized multiscale energy and vorticity analysis (MS-EVA), the all-year-round atmospheric blockings over the Atlantic are investigated to gain insight into the underlying dynamical processes. The atmospheric fields are first reconstructed onto three scale ranges or scale windows, namely, the basic flow window, blocking window, and synoptic window, and then the MS-EVA is performed. The reconstructed blocking events are selected out and a composited event is formed henceforth, which shows a clear wavelike signal on the blocking window. With the same compositing criterion, the multiscale energetics, including multiscale transports, interscale canonical transfers, buoyancy conversions, among others, are also composited to form a complete Lorenz cycle. From the result it is found that a lifecycle of the blocking scale kinetic energy (KE) may be divided into three phases: onset phase, amplification phase, and decay phase, each with distinct mechanisms in play. In the onset phase, the blocking is generated from a collaboration of pressure work and the canonical transfer of kinetic energy from the synoptic scale window, while in the amplification phase, the upscale canonical transfer from the synoptic eddies dominates. The blocking decays as the system transports the blocking-scale KE away and, most importantly, as it converts the blocking-scale KE into the blocking-scale available potential energy (APE) through buoyancy conversion.
keywords:multiscale window transform, localized multiscale energy and vorticity analysis, canonical transfer, blocking, upscale feedback
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