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

北太平洋急流季节内涨落的结构、演化和生命周期

• 批准号: 1265182
• 负责人: Jonathan Martin
• 金额: $ 64.47万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2017-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1265182&HistoricalAwards=false
• 关键词: Structure; Evolution; Life; Cycles; Intraseasonal

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.

这项工作的目的是通过统计、天气气候学和个案研究分析的结合，大大增加我们对冬季太平洋急流变化的认识。对流层上层急流作为天气尺度天气系统与大尺度环流交界的主要现象，对区域气候具有特别强的调节作用。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率的了解还远远不够完整。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，研究小组将确定太平洋急流主要变率模态之间的首选转换；这一结果将为构建与每种首选过渡物种相关的全盆地结构、演化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退缩气候学，考察了西伯利亚/欧亚板块对流层低层冷空气面积范围与太平洋急流纬向范围之间的关系。由于太平洋急流是极地急流和副热带急流的混合体，再分析数据也将用于检查这两个组成部分在确定的急流缩回情况下的行为，作为将缩回事件分离为主要由温带和热带变率引起的事件的第一步。最后，为了更好地了解它们潜在的大尺度和天气尺度动力学，将使用NCAR天气研究与预报（WRF）模式，利用对选定案例的精细尺度数值模拟的输出，对两个代表性的喷气机缩回进行详细的案例研究分析。该项目将揭示冬季太平洋急流的变化；这对夏威夷州和西海岸的预报也有帮助。因此，这个项目的广泛影响是巨大的。