Winds and the Weather: Evaluating Three Dimensional (3D) Stratospheric / Tropospheric Jet Relationships and Their Roles in Extreme Cool-Season Weather Events

平流层是大气的一层，温度随高度的增加而增加，阻止垂直运动，从而阻止进入在对流层形成的云、风暴和锋面天气系统。然而，非常长的波可以从对流层传播到平流层并影响其环流，最显著的是通过破坏其极地涡旋并引起平流层突然变暖（SSW）事件。相反，平流层环流可以对对流层天气产生实质性影响，尽管是通过尚未完全了解的间接途径。特别是有几项研究表明，当平流层环极涡旋较弱或被南纬槽干扰时，冷空气爆发（CAOs）的可能性更大，平流层涡旋的状况也可能影响对流层急流，进而影响地面天气。因此，平流层和对流层之间的相互作用不仅具有科学意义，而且具有实际意义，是大量研究工作的重点。该奖项下的研究使用新颖的方法来表征平流层-对流层相互作用的三维结构。这项工作补充了以前的研究，这些研究强调空间聚集量，如平流层涡旋在极帽上的平均强度和对流层喷流在纬度圈上的平均速度。半球平均足以识别SSW，但它可能掩盖事件结构上的差异，这些差异对其与对流层的相互作用很重要。例如，从半球平均的角度来看，平流层涡旋可能会减弱，因为涡旋中心已经远离了极点，或者因为涡旋实际上已经分裂成两个不同的涡旋。分裂涡旋和位移涡旋可能以不同的方式影响对流层。它们对喷射流的影响也可能取决于喷射速度的纵向变化，这种变化会被一个纬度圈的平均所掩盖。这项工作主要包括分析由首席研究员开发的两个数据集中确定的平流层-对流层相互作用。一个是JETPAC，即JEt和对流层顶产品的分析和表征，它在包括对流层和平流层下层在内的三维网格上识别急流最大值的位置，并在每个网格柱中识别对流层顶（或多个对流层）。第二个是使用称为CAVE-ART的算法开发的，用于使用区域跟踪算法表征和分析漩涡演化。CAVE-ART使用计算机视觉方法来识别平流层极地涡旋的三维结构。CAVE-ART能够在分裂的SSW事件中跟踪漩涡的单独碎片。这项工作具有更广泛的影响，因为它与重大天气事件（如CAOs）有关。为该项目生成的数据集可供研究界使用，以便最大限度地发挥其对科学发现的价值。开发了基于网络的外联材料，并用于向公众进行外联，这项工作支持了新墨西哥理工大学的两名学生。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智力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 stratosphere is a layer of the atmosphere where the increase of temperature with height discourages vertical motions, thereby barring entry to the clouds, storms, and frontal weather systems that form in the troposphere below. Nevertheless very long waves can propagate from the troposphere into the stratosphere and influence its circulation, most dramatically by disrupting its circumpolar vortex and causing a sudden stratospheric warming (SSW) event. Conversely, the stratospheric circulation can have a substantial effect on tropospheric weather, albeit through indirect pathways which are not entirely understood. In particular several studies have shown that cold air outbreaks (CAOs) are more likely when the stratospheric circumpolar vortex is weak, or disrupted by an SSW, and the condition of the stratospheric vortex can also influence the tropospheric jet streams in ways that can in turn affect surface weather. Interactions between the stratosphere and troposphere are thus of practical as well as scientific importance and are a focus of substantial research effort.Research under this award uses novel methods to characterize the three-dimensional structure of stratosphere-troposphere interactions. The work complements previous studies which have emphasized spatially aggregated quantities like the mean strength of the stratospheric vortex averaged over the polar cap and the mean speed of tropospheric jets averaged around circles of latitude. A hemispheric average can suffice to identify an SSW but it may conceal differences in the structure of the event which matter for its interactions with the troposphere. For instance the stratospheric vortex can be weaker in a hemispherically-averaged sense because the vortex center has moved away from the pole, or because the vortex has in fact split into two distinct vortices. A split vortex and a displaced vortex are likely to influence the troposphere in different ways. Their influence on jet streams may also depend on longitudinal variations in jet speed that would be obscured by averaging around a latitude circle.The work consists primarily of analysis of stratosphere-troposphere interactions identified in two datasets developed by the Principal Investigators. One is called JETPAC, for JEt and Tropopause Products for Analysis and Characterization, which identifies the locations of jet stream maxima on a three-dimensional grid including the troposphere and lower stratosphere and also identifies the tropopause (or multiple tropopauses) in each grid column. The second is developed using an algorithm called CAVE-ART, for Characterization and Analysis of Vortex Evolution using Algorithms for Region Tracking. CAVE-ART uses methods from computer vision to identify the three-dimensional structure of the stratospheric polar vortex. CAVE-ART is able to track separate pieces of the vortex in the event of a splitting SSW event.The work has broader impact due its relevance to significant weather events such as CAOs. The datasets generated for the project are made available to the research community in order to maximize their value for scientific discovery. Web-based outreach materials are developed and used to conduct outreach to the public, and the work supports two students at New Mexico Tech.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.