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

平流层是大气层中的一层，温度随高度的增加阻碍了垂直运动，从而阻止了在对流层下面形成的云，风暴和锋面天气系统的进入。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，最显着的是破坏其环极涡旋，并导致突然的平流层变暖（SSW）事件。 相反，平流层环流可以对对流层天气产生重大影响，尽管是通过不完全理解的间接途径。 特别是，一些研究表明，当平流层绕极涡旋较弱或被SSW破坏时，更有可能发生冷空气爆发（CAO），并且平流层涡旋的状况也会影响对流层急流，从而影响对流层急流。影响地面天气。 因此，平流层和对流层之间的相互作用具有实际和科学的重要性，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，强调空间聚集的量，如平流层涡旋的平均强度平均在极冠和对流层急流的平均速度平均周围的圈的纬度。 半球平均值足以识别SSW，但它可能掩盖了事件结构的差异，这对它与对流层的相互作用很重要。 例如，平流层涡旋在半球平均的意义上可能较弱，因为涡旋中心已经远离极点，或者因为涡旋实际上已经分裂成两个不同的涡旋。分裂涡和位移涡可能以不同的方式影响对流层。它们对急流的影响也可能取决于急流速度的纵向变化，而这种变化会被纬度圈周围的平均值所掩盖。这项工作主要包括对主要研究人员开发的两个数据集中确定的平流层-对流层相互作用进行分析。 一种称为JETPAC，用于分析和表征的JEt和对流层顶产品，它确定了包括对流层和平流层下部在内的三维网格上急流最大值的位置，并确定了每个网格列中的对流层顶（或多个对流层顶）。 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旋涡演化。 CAVE-ART使用计算机视觉方法来识别平流层极涡的三维结构。CAVE-ART能够在SSW分裂事件中跟踪涡旋的各个部分。由于其与CAO等重大天气事件的相关性，这项工作具有更广泛的影响。为该项目生成的数据集可供研究界使用，以最大限度地发挥其对科学发现的价值。 基于网络的推广材料的开发和使用进行外展到公众，并支持两名学生在新墨西哥州技术的工作。这个奖项反映了NSF的法定使命，并已被认为是值得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的支持。

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.