The Structure, Evolution, and Life Cycles of Intraseasonal Fluctuations of the North Pacific Jet Stream

这项工作的目的是通过统计、天气气候和个例研究分析的结合，大大增加我们对冬季太平洋急流变率的了解。高空急流是天气尺度天气系统与大尺度环流界面上的主要现象，对区域气候有着特别强的控制作用。尽管冬季太平洋急流对太平洋盆地内外的敏感天气和大尺度环流都有重大影响，但目前对其季节内变化的理解还远未完成。在之前的工作中，该团队已经确定了这种可变性的两种主要模式。在这个项目中，该小组将确定太平洋急流的主要变化模式之间的首选过渡;其结果将为构建与每个首选过渡物种相关的全流域结构，演变和天气特征的复合材料提供信息。 利用相空间分析扩展急流收缩气候学，研究西伯利亚/欧亚地区对流层低层冷空气的分布范围与太平洋急流的纬向分布之间的关系。由于太平洋急流是极地和副热带急流的混合体，再分析数据也将被用来检查这两个组件的行为，在确定的情况下，喷流回缩作为第一步，隔离人口的回缩事件到那些被迫主要由热带和热带的变化，分别。最后，为了更好地了解其基本的大尺度和天气尺度动力学，将使用NCAR天气研究和预报（WRF）模型对两个典型的喷流回缩案例进行详细的案例研究分析，这些案例采用了对选定案例进行细尺度数值模拟的结果。该项目将深入了解冬季太平洋急流的变化;这对改善夏威夷州和西海岸的预测具有影响。因此，该项目的广泛影响是巨大的。

The work aims to substantially increase our knowledge of wintertime Pacific jet variability through a combination of statistical, synoptic-climatological and case study analyses. As the primary phenomenon at the interface between synoptic-scale weather systems and the large-scale circulation, upper tropospheric jets are particularly strong governors of regional climate. Despite the substantial influence that the wintertime Pacific jet has on both sensible weather and large-scale circulation within and beyond the Pacific basin, current understanding of its intraseasonal variability is far from complete. In prior work the team has identified two leading modes of this variability. In this project the team will identify preferred transitions between the leading modes of variability of the Pacific jet; the results of this will inform construction of composites of the basin-wide structure, evolution and weather features associated with each species of preferred transition. Using the phase space analysis to expand the jet retraction climatology, the relationship between the areal extent of lower tropospheric cold air over the Siberia/Eurasia sector and the zonal extent of the Pacific jet will be examined. Since the Pacific jet is a hybrid of the polar and subtropical jets, reanalysis data will also be used to examine the behavior of these two components in identified cases of jet retraction as a first step toward segregating the population of retraction events into those forced primarily by extratropical and tropical variability, respectively. Finally, in order to better understand their underlying large- and synoptic-scale dynamics, detailed case study analyses of two representative cases of jet retraction employing output from fine-scale numerical simulations of the selected cases will be undertaken using the NCAR Weather Research and Forecasting (WRF) model. This project will shed insights into wintertime Pacific jet variability; this has implications for improved prediction for the state of Hawaii as well as the west coast. Thus the broader impacts of this project are substantial.