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

平流层是位于云层和风暴之上的大气层，影响着地球表面的天气。但是，尽管处于天气之上，平流层仍然影响着天气，特别是当冬季在极地帽上形成的向东移动的涡旋在称为平流层突然变暖（SSWs）的事件中破裂时。预计对流层对南纬压风的响应是极地帽上的高地表压力，更频繁地发生冷空气爆发，以及更频繁地发生沿海东北风暴。因此，ssw对亚季节到季节（S2S）天气预报非常有兴趣，ssw影响地面天气的机制已经得到了深入研究。该奖项的工作旨在提高对ssw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面天气的影响的理解。一个关键的问题是，一些ssw对下层对流层有很强的影响，而另一些则没有，并且地表温度异常的分布可能因极地涡旋破坏而大不相同。主要研究人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。例如，在一些SSWs中，在平流层极涡破裂后会形成一个“子”涡，而地面温度响应可能会因子涡的位置而变化。该研究包括对观测数据集的分析，耦合模式比对项目（CMIP）提供的模拟输出，以及亚季节到季节（S2S）预测和隐藏组合，包括国家多模式组合（NMME）提供的预测和隐藏组合。理想湿润大气模式（MIMA）是一种简化的模式，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。实验是通过使用人工阻力来诱导具有特定地理畸变的涡旋破坏，以便评估其对地表温度的影响。鉴于平流层涡旋破坏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。其中一名主要研究人员维护了一个博客，作为北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）根据国家科学基金会和BSF之间的谅解备忘录共同资助的项目。该协议允许美国和以色列研究人员提交一份单一的合作提案，并由NSF进行同行评审。在国家科学基金会的评审结果和认可的国家科学基金会项目的推荐下，每个机构资助预算的比例和与自己国家有关的调查人员。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知识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 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.