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Intraseasonal oscillations in the Earth-atmosphere system.

机译：地球大气系统中的季节内振荡。

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摘要

Intraseasonal fluctuations in the Earth's angular momentum budget are studied using 12-year overlapping records of length-of-day (LOD) variations from the Jet Propulsion Laboratory and atmospheric angular momentum (AAM) data from the National Meteorological Center (NMC), as well as the results of three-year (with mountains) and one-year (without mountains) perpetual-January simulations of the global atmosphere, performed with the UCLA General Circulation Model (GCM).; Two distinct oscillations, with periods of 50 and 40 days, are found in the observed series of LOD and global AAM. Regional analysis of the NMC data shows that the stronger 50-day oscillation arises from zonal wind variations in the tropics, presumably associated with the Maddan-Julian (MJ) oscillation, while the 40-day oscillation originates in the Northern Hemisphere (NH) extratropics. Evidence of tropical-extratropical interaction in the 36-60 day band, especially prominent in a case study of the strong global oscillations occurring in early 1988, is derived from auto-spectral and cross-spectral analysis of the AAM data by latitude.; A 42-day AAM oscillation arises in the NH extratropics of the three-year GCM run, characterized by a 300-day amplitude fluctuation cycle which strongly resembles that found in the same region from the NMC data. These similarities indicate that the observed NH extratropical oscillation is dynamically independent of the equatorially-trapped MJ oscillation, which is absent from this version of the GCM. A barotropic, zonally-symmetric oscillation occurs in the model tropics, driven by mass exchange with the NH extratropics; localized tropical-extratropical teleconnections are also found, resembling patterns observed by previous investigators to be linked with intraseasonal convective activity in the tropics.; A standing, wavenumber-two oscillation occurring at 500 mb in the NH extratropics was found to undergo tilted-trough vacillation in conjunction with the model's AAM cycle. During the extreme phases of the AAM oscillation the height anomalies tilt southwest-northeast, generating little net mountain torque, while during the phases of rapid AAM change they tilt northwest-southeast, producing strong mountain torques over the Rockies and Himalayas. No AAM oscillations were found in the one-year run of the model without mountains, confirming the topographic origin of the AAM oscillation in the NH extratropics.
机译：使用喷气推进实验室的12天重叠记录的日长（LOD）以及国家气象中心（NMC）的大气角动量（AAM）数据，研究了地球角动量预算的季节内波动。是使用UCLA总循环模型（GCM）对全球大气进行的永久（一月）和三年（无山）和一年（无山）模拟的结果。在观察到的LOD和全局AAM系列中发现了两个分别为50天和40天的振荡。 NMC数据的区域分析显示，热带地区纬向风的变化引起了更强的50天振荡，大概与Maddan-Julian（MJ）振荡有关，而40天振荡起源于北半球温带。在36-60天范围内，热带与热带之间的相互作用的证据，特别是在1988年初发生的强烈全球振荡的案例研究中尤为突出，这是根据纬度对AAM数据进行的自动光谱和跨光谱分析得出的。三年GCM运行的NH温带中出现了42天的AAM振荡，其特征是300天的振幅波动周期，与NMC数据在同一地区发现的振幅波动周期非常相似。这些相似之处表明，观测到的NH温控振荡是动态独立于赤道陷井MJ振荡的，而该版本的GCM则没有这种振荡。在模型热带中，正压，纬向对称振荡是由与NH温体系的质量交换驱动的。还发现了局部热带-热带外向遥相关，类似于以前的研究人员观察到的模式与热带地区的季节内对流活动有关。发现在NH温带地区500 mb处发生的驻波，第二波振荡与模型的AAM周期一起经历了斜槽波动。在AAM振荡的极端阶段，高度异常向西南偏北倾斜，产生的净山扭矩很小，而在AAM快速变化的阶段中，它们向西北偏东南倾斜，从而在落基山脉和喜马拉雅山脉上产生强烈的山脉扭矩。在没有山脉的模型的一年运行中未发现AAM振荡，这证实了NH温带地区AAM振荡的地形起因。

著录项

  • 作者

    Marcus, Steven Leonard.;

  • 作者单位

    University of California, Los Angeles.;

  • 授予单位 University of California, Los Angeles.;
  • 学科 Physics Atmospheric Science.; Geodesy.
  • 学位 Ph.D.
  • 年度 1990
  • 页码 210 p.
  • 总页数 210
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 大气科学（气象学）;大地测量学;
  • 关键词

  • 入库时间 2022-08-17 11:50:32

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