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

北太平洋上空的急流对越洋登陆美国和加拿大海岸的冬季风暴过程施加了控制作用。急流作为风暴传送带的作用使其成为天气预报员感兴趣的话题，因为风暴的路径和强度对各种形式的急流变化很敏感，包括扩展、收缩和南北弯曲。也许更重要的是，喷气机的变化可以影响连续的风暴，因此喷气机波动的影响超出了典型的五天预测，进入了亚季节预测的领域。但是，太平洋急流变化的潜在动力尚未得到很好的理解，有关机制的基本问题仍然存在。太平洋扇区的不同寻常之处在于，它结合了中纬度急流动力学，其特点是急流与沿其移动的天气模式之间的相互作用，以及来自西太平洋温暖水域上空深层对流区域的低纬度影响。在早期的工作中，一位首席研究员使用线性逆模式（LIM）来确定热带影响与中纬度动力相互作用从而产生高层环流异常的机制。在本工作中，LIM分析被应用于理解使用自组织图（SOMs）识别的射流波动。工作的重点是从一种喷射状态过渡到另一种状态的动力学，以及这种过渡对下游天气的影响。如上所述，这项工作与北美天气有关，与长期预报有关，因此具有社会和科学意义。此外，ppi还参与公共宣传活动，包括威斯康星州公共广播电台每月一期的节目。该项目还为两名研究生和两名本科生暑期实习生提供支持和培训。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The jet stream over the North Pacific exerts a controlling influence on the procession of winter storms that cross the ocean to make landfall on the US and Canadian coasts. The role of the jet as a conveyor of storms makes it a topic of interest for weather forecasters as the paths and intensities of the storms are sensitive to the various forms of jet variability including extension, retraction and north-south meandering. Perhaps more importantly, jet variations can affect a succession of storms, so the influence of jet fluctuations extends beyond the typical five-day forecast and into the domain of subseasonal prediction. But the underlying dynamics of Pacific jet variations are not well understood and fundamental questions remain as to the mechanisms involved.The Pacific sector is unusual in its combination of middle-latitude jet dynamics, featuring the interplay between the jet and the weather patterns that move along it, and low-latitude influences from the region of deep convection over the warm waters of the western Pacfic. In earlier work one of the Principal Investigators (PIs) used a Linear Inverse Model (LIM) to identify a mechanism through which tropical influences interact with middle-latitude dynamics to produce upper-level circulation anomalies. In the present work the LIM analysis is applied to understand jet fluctuations identified using Self-Organizing Maps (SOMs). The work focuses on the dynamics of transitions from one jet state to another and the consequences of the transitions for downstream weather.The work is of societal as well as scientific interest given its connection to North American weather and relevance to long-range forecasting, as noted above. In addition, the PIs engage in public outreach including a monthly show on Wisconsin Public Radio. The project also provides support and training for two graduate students and two undergraduate summer interns.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.