Collaborative Research: NSF-BSF--Tropospheric Response to Zonal Asymmetry of the Stratospheric Polar Vortex and Its Aapplication to Subseasonal to Seasonal (S2S) Prediction

平流层是位于影响地球表面天气的云层和风暴上方的大气层。 但是，尽管平流层位于天气之上，但它仍然会影响天气，特别是当冬季在极冠上空形成的向东移动的涡旋在称为平流层突然变暖（SSW）的事件中崩溃时。 预计对流层对SSW的反应是极冠上空的表面压力更高、冷空气爆发更频繁以及沿海东北风暴更频繁。因此，SSW 对于次季节到季节性 (S2S) 天气预报非常重要，并且 SSW 影响地表天气的机制已得到深入研究。该奖项的工作旨在增进对南海风暴和其他不太极端的平流层极地涡旋干扰对对流层环流和地表天气影响的了解。 一个关键问题是，一些南海风对底层对流层有强烈影响，而另一些则不然，而且一种极地涡旋干扰与另一种极地涡旋干扰的表面温度异常分布可能有很大不同。 首席研究员假设对流层响应的差异部分是由于极地涡旋破坏过程中发生的扭曲模式造成的。 例如，在一些SSW中，平流层极地涡旋分解后会形成“子”涡旋，并且表面温度响应可能会根据子涡旋的位置而变化。该研究涉及对观测数据集的分析、通过耦合模型比对项目（CMIP）提供的模拟输出，以及次季节到季节（S2S）预报和播报的集合，包括通过国家多模式集合提供的预报和播报。 （NMME）。 理想化潮湿大气模型 (MIMA) 的模拟对数据分析工作进行了补充，该模型是一个简化模型，能够模拟北半球冬季环流的真实特征，包括急流、驻波和平流层极地涡旋。 实验通过使用人工阻力来诱发具有特定地理扭曲的涡旋扰动，以便评估它们对地表温度的影响。鉴于平流层涡旋扰动与极端冬季天气之间的联系，这项工作具有社会和科学意义。 一位首席研究员维护着一个博客，作为北半球当前和预测天气模式的技术和非技术讨论的门户。 该项目还为一名研究生和一名博士后提供支持和培训。这是一个由美国国家科学基金会地球科学理事会（NSF-GEO）和以色列两国科学基金会（BSF）根据 NSF 和 BSF 谅解备忘录中的语言共同资助的项目。该协议允许由美国和以色列调查人员提交一份单一的合作提案并由 NSF 进行同行评审。根据 NSF 绩效审查的成功结果以及认可的 NSF 计划推荐的奖项，每个机构都会资助与其本国相关的预算和研究人员的比例。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点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 the layer of the atmosphere that sits above the clouds and storms that affect weather at the earth's surface. But despite being above the weather the stratosphere still influences the weather, particularly when the eastward-moving vortex that forms in winter over the polar cap breaks down in events called sudden stratospheric warmings (SSWs). The expected tropospheric response to an SSW is higher surface pressure over the polar cap, more frequent occurrence of cold air outbreaks, and and more frequent coastal Nor'easter storms. SSWs are thus of great interest for subseasonal to seasonal (S2S) weather prediction, and the mechanisms through which SSWs influence surface weather have been intensively studied. Work under this award seeks to improve understanding of the effects of SSWs and other less extreme stratospheric polar vortex disruptions on tropospheric circulation and surface weather. A key issue is that some SSWs have a strong effect on the underlying troposphere while others do not, and the distribution of surface temperature anomalies can be quite different from one polar vortex disruption to another. The Principal Investigators hypothesize that differences in the tropospheric response are due in part to the pattern of distortions that occur over the course of a polar vortex disruption. For instance in some SSWs a "daughter" vortex forms after the stratospheric polar vortex breaks down, and the surface temperature response could vary depending on the location of the daughter vortex.The research involves analysis of observational datasets, output from simulations available through the Coupled Model Intercomparison Project (CMIP), and ensembles of subseasonal to seasonal (S2S) forecasts and hidcasts including those available through the National Multi-Model Ensemble (NMME). The data analysis effort is complemented by simulations from the Model of an Idealized Moist Atmosphere (MIMA), a simplified model capable of simulating realistic features of the Norhtern Hemisphere winter circulation including jet streams, stationary waves, and the stratospheric polar vortex. Experiments are conducted by using an artificial drag force to induce vortex disruptions with specific geographical distortions so that their effects on surface temperature can be assessed.The work is of societal as well as scientific interest given the connection between stratospheric vortex disruptions and extreme winter weather. One of the Principal Investigators maintains a blog that serves as a portal for technical and non-technical discussion of present and forecasted weather patterns for the Northern Hemisphere. The project also provides support and training for a graduate student and a postdoctoral associate.This is a project jointly funded by the National Science Foundation's Directorate of Geosciences (NSF-GEO) and the Israel Binational Science Foundation (BSF) in accord with the language in the Memorandum of Understanding between the NSF and the BSF. This Agreement allows a single collaborative proposal, involving US and Israeli investigators, to be submitted and peer-reviewed by NSF. Upon successful results of the NSF merit review and recommendation by the cognizant NSF Program of an award, each Agency funds the proportion of the budget and the investigators associated with its own country.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.