Low-Frequency Variability of Troposphere-stratosphere Coupling

9405448 Baldwin从一周到年际的时间尺度上，对流层气流模式有相当大的变化。这项研究的重点是了解对流层中的平稳波模式可以解释多少平流层的低频变化。一般的方法是确定对流层中部与平流层气流有关的模式。将特别注意厄尔尼诺/南方涛动（ENSO）对平流层可能产生的影响，这种影响可能通过调节温带对流层气流来传达。PI将使用对流层高度场的经验正交函数（EOF）分析和奇异值分解（SVD）分析，以及相关分析、复合分析和光谱分析来识别在年际和季节间时间尺度上似乎对平流层有显著影响的模态。还将使用互补的非线性聚类分析技术。本文将利用简化物理的GCM进行一系列实验，研究中层大气对对流层环流异常的响应。这些实验将用于确定该模式对对流层异常模式的平流层响应。将模式冬季平流层的响应与数据分析的结果进行比较，将提供一种有价值的方法来确定对流层异常对冬季平流层年际变率的贡献。作为这项研究的一部分，PI将使用网格化的ECMWF数据分析，结合雷达探空仪数据，确定热带对流层水平波结构，以更好地阐明热带对流层中存在的不同类型的天气尺度扰动及其与平流层的垂直耦合（如果有的话）。重点是热带低层大气中有组织的、向西行进的天气尺度波，这些波可能参与了罗斯重力波的激发。我们将研究对流层下层和上层的扰动，以及两层之间的垂直耦合。这项研究很重要，因为它将增强我们对与平流层-对流层动力学相关的重要气候过程的理解。

9405448 Baldwin On timescales from a week through interannual there is considerable variability of tropospheric flow patterns. This study will focus on understanding how much of the low-frequency variability of the stratosphere can be accounted for by stationary wave patterns in the troposphere. The general approach will be to identify patterns in the mid-troposphere that are linked with stratosphere flow. Particular attention will be paid to the possible influences of El Nino/Southern Oscillation (ENSO) on the stratosphere that may be communicated through modulation of the extratropical tropospheric flow. The PI will use empirical orthogonal function (EOF) analysis and singular value decomposition (SVD) analysis of the tropospheric height field together with correlations, composites and spectral analysis to identify modes which, on interannual and interseasonal timescales, seem to have a significant stratospheric influence. The complementary nonlinear technique of cluster analysis will also be used. A series of experiments using a GCM with simplified physics will be used to study the response of the middle atmosphere to tropospheric circulation anomalies. The experiments will be designed to determine the model's stratospheric response to tropospheric anomaly patterns. Comparing the response of the model's winter stratosphere with the resultq of the data analysis should provide a valuable method of identifying the contribution to winter stratospheric interannual variability from tropospheric anomalies. As part of this study the PI will use gridded ECMWF data analyses in conjunction with rawinsonde data, to determine tropical tropospheric horizontal wave structure to better elucidate the different types of synoptic-scale disturbances that exist in the tropical troposphere and their vertical coupling, if any, to the stratosphere. The focus is specifically on organized, westward- traveling, synoptic-scale waves in the tropical lower atmosphere that may be involved in the excitation of Rossby-gravity waves. Disturbances in both lower and upper troposphere will ne investigated, as will any vertical coupling between the two layers. This research is important because it should enhance our understanding of important climate processes related to stratospheric-tropospheric dynamics.