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

平流层是位于云和风暴之上的大气层，这些云和风暴影响着地球表面的天气。 但是，尽管平流层在天气之上，平流层仍然影响天气，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）的事件中破裂时。 预计对流层对SSW的反应是极盖上方更高的表面压力，更频繁地发生冷空气爆发，以及更频繁的沿海东北风暴。因此，SSWs是非常感兴趣的亚季节到季节（S2 S）的天气预报，并通过SSWs影响地面天气的机制进行了深入研究。该奖项下的工作旨在提高对SSW和其他不太极端的平流层极涡破坏对流层环流和地面天气的影响的理解。 一个关键的问题是，一些SSW有一个强大的底层对流层的影响，而其他人没有，和表面温度异常的分布可以是完全不同的从一个极涡破坏到另一个。 主要研究人员假设对流层响应的差异部分是由于极涡破坏过程中发生的扭曲模式。 例如，在一些SSW中，平流层极涡破裂后会形成“子”涡，并且表面温度响应可能会根据子涡的位置而变化。研究涉及对观测数据集的分析，通过耦合模式相互比较项目（CMIP）提供的模拟输出，以及子季节到季节（S2 S）预报和隐藏预报的集合，包括通过国家多模式Ensemble（NMME）提供的那些。 理想化湿大气模型（米马）的模拟补充了数据分析工作，这是一个简化的模型，能够模拟北半球冬季环流的现实特征，包括急流，驻波和平流层极涡。 通过使用人工拖曳力进行实验，以引起具有特定地理扭曲的涡旋破裂，从而可以评估其对地面温度的影响，鉴于平流层涡旋破裂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。 其中一名首席调查员维护着一个博客，作为北方半球目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助理提供支持和培训，这是一个由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）共同资助的项目，符合国家科学基金会和BSF之间谅解备忘录的雅阁。该协议允许一个单一的合作建议，涉及美国和以色列的调查人员，提交和同行评审的NSF。在NSF的价值评估和认可的NSF计划推荐奖项的成功结果后，每个机构资助与其本国相关的预算和调查人员的比例。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响评估标准进行评估，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.