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穿越大洋登陆美国和加拿大海岸的冬季风暴进程产生了控制性的影响。急流作为风暴传送器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急流的各种形式的可变性很敏感，包括伸展、收缩和南北蜿蜒。也许更重要的是，急流变化可能会影响一系列风暴，因此急流波动的影响超出了典型的五天预报，进入了亚季节性预报领域。但太平洋急流变化的基本动力机制仍未得到很好的了解，其中涉及的基本问题仍然存在。太平洋部分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，以及西太平洋温暖水域上深对流区的低纬影响。在早期的工作中，其中一位首席调查人员(PI)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产生高层环流异常的机制。在目前的工作中，LIM分析被用来理解使用自组织映射(SOM)识别的喷流波动。这项工作的重点是从一种喷流状态到另一种喷流状态的转变动力学以及这种转变对下游天气的影响。如上所述，鉴于其与北美天气的联系以及与长期预报的相关性，这项工作具有社会和科学意义。此外，PI还参与公共宣传活动，包括每月在威斯康星州公共广播电台播出一档节目。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NSF的法定使命，并通过使用基金会的智力优势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.